Transcript for NASASciFiles - The Case of the Powerful Pulleys

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HI, I'M DANNY TREJO,
AND I PLAY UNCLE MACHETE

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IN THE BLOCKBUSTER MOVIES
SPY KIDS AND SPY KIDS II.

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AS SUPERSPIES, THE SPY KIDS HAVE
TO USE ALL KINDS OF EXCITING GIZMOS

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AND GADGETS TO HELP SAVE THE WORLD,

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BUT THE REAL EXCITEMENT
BEGINS IN THE CLASSROOM

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AS YOU LEARN HOW THOSE GIZMOS
AND GADGETS REALLY WORK.

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SO YOU WON'T WANT TO MISS
THE NEXT BIG ADVENTURE

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AS THE TREE HOUSE DETECTIVES USE
SCIENCE, MATH, AND TECHNOLOGY

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TO REVEAL THE SECRETS OF
SIMPLE MACHINES IN ORDER

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TO HELP JACOB BACK
IN THE TREE HOUSE.

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YOU CAN SEE IT ALL IN THIS
EPISODE OF NASA SCI FILES:

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THE CASE OF THE POWERFUL PULLEYS.

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COME ON, NOW, AND LEARN ABOUT
MATH, SCIENCE, AND TECHNOLOGY.

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NASA SCI FILES.

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DISCOVERING THE WORLD WE'RE
IN, DOING COOL EXPERIMENTS.

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NASA SCI FILES.

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NASA SCI FILES.

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NASA SCI FILES.

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DON'T FORGET TO ANSWER
THE FOLLOWING QUESTIONS:

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WHAT IS ENERGY?

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WHAT DOES IT MEAN TO DO WORK?

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WHAT ARE SIMPLE MACHINES?

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WHEN YOU SEE THIS ICON,
THE ANSWER IS NEAR.

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CHECK THIS OUT.

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JACOB, WATCH OUT!

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JACOB?

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JACOB?

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YOU GOT GAFFED.

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THE DOCTOR SAYS I'LL HAVE TO WEAR
THIS CAST FOR SIX TO EIGHT WEEKS.

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I'M SURE IT'S TOUGH
GETTING AROUND IN A CAST.

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YEAH, I GUESS YOU HAVE
TO TAKE IT NICE AND EASY.

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WELL, GETTING AROUND IS STILL OKAY,

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BUT I REALLY MISS BEING
IN THE TREE HOUSE.

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YOU ARE NOT CLIMBING
UP INTO THE TREE HOUSE.

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SHE'S RIGHT, JACOB.

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CLIMBING INTO THE TREE
HOUSE WOULD BE A BAD IDEA.

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I'M NOT GOING TO CLIMB
INTO THE TREE HOUSE.

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BUT YOU GUYS DON'T KNOW WHAT IT'S
LIKE BEING STUCK IN THIS CAST.

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THE TREE HOUSE IS
LIKE MY SECOND HOME.

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MAYBE WE CAN FIGURE OUT A WAY TO
GET YOU BACK INTO THE TREE HOUSE

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WITHOUT CLIMBING THE LADDER.

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YOU MIGHT BE ON TO
SOMETHING, BIANCA.

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STOP JOKING, YOU GUYS.

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YOU'RE GETTING MY HOPES UP.

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WE'RE NOT JOKING.

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AFTER ALL, WE ARE THE
TREE HOUSE DETECTIVES.

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IT MIGHT TAKE A LITTLE WHILE,
BUT WE CAN SOLVE THE PROBLEM.

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I CAN'T WAIT TO GET BACK
INTO THE TREE HOUSE.

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DON'T WORRY, JACOB.

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I'M SURE WE'LL HAVE YOU BACK IN
THE TREE HOUSE IN NO TIME AT ALL.

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THIS PROBLEM MAY BE
TOUGHER THAN WE THOUGHT.

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LET'S BRAINSTORM.

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MAYBE WE COULD USE A
ROPE TO PULL JACOB UP.

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OR MAYBE A TRAMPOLINE.

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A TRAMPOLINE?

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THAT'S SILLY.

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REMEMBER, THERE'S NO
CRITICISM WHEN YOU BRAINSTORM.

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WHAT ABOUT LOWERING THE TREE HOUSE?

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OR WE COULD CARRY HIM UP.

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HOW MUCH DOES JACOB WEIGH?

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PROBABLY ABOUT 90 POUNDS.

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WELL, THAT'S NOT TOO MUCH.

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THEN LET'S TRY MY IDEA OF
LIFTING HIM WITH A ROPE.

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LET'S GIVE IT A TRY.

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CAN WE DO THIS LATER
THIS AFTERNOON?

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BIANCA AND I ARE GOING TO
SANDY BOTTOM NATURE PARK

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WITH MY SISTER'S GIRL SCOUT TROOP.

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DR. "D" IS DOING SOME
PHYSICS EXPERIMENTS.

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SURE.

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SEE YOU THIS AFTERNOON.

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BYE.

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IT TAKES ENERGY TO DO WORK.

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ENERGY COMES IN A VARIETY OF FORMS.

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THE POWDER IN THIS FUNNEL
HAS POTENTIAL ENERGY.

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IT'S CHANGED INTO HEAT ENERGY
WHEN I BLOW IT THROUGH THIS FLAME.

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IF I DO WORK AND USE MY ENERGY
TO STRETCH THIS GIANT SLINGSHOT,

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THE ENERGY IS STORED AS
ELASTIC POTENTIAL ENERGY.

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THEN WHEN I LET GO, THE
ENERGY IS CHANGED INTO ENERGY

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OF MOTION, OR KINETIC ENERGY.

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FINALLY...

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SPLAT!

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PLEXIGLAS DID THE WORK
TO STOP THE TOMATO.

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IT TAKES A LOT OF WORK TO
LIFT THIS 25-KILOGRAM ANVIL.

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I HAVE TO OVERCOME
THE PULL OF GRAVITY.

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THE ANVIL NOW HAS A LOT OF
GRAVITATIONAL POTENTIAL ENERGY.

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THIS POOR CANTALOUPE
WILL BE SMASHED

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WHEN I RELEASE THE
ENERGY BY LETTING GO.

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HI, DR. "D."

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THAT WAS A GREAT SHOW.

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I REALLY LIKED THE EXPERIMENTS.

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THANKS.

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BY THE WAY, ARE YOU
WORKING ON ANY PROJECTS?

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WELL, JACOB HAS BROKEN HIS FOOT,
SO WE'RE TRYING TO FIGURE OUT A WAY

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TO GET HIM BACK INTO
THE TREE HOUSE.

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WE THINK WE CAN LIFT
HIM WITH A ROPE.

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IF WE ALL WORK TOGETHER.

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LET'S TALK A LITTLE BIT ABOUT WORK.

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FIRST, YOU HAVE TO HAVE A
FORCE, A PUSH OR A PULL.

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BUT FORCE ALONE IS NOT ENOUGH.

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TO DO WORK, THE FORCE MUST BE
APPLIED THROUGH A DISTANCE.

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HERE, HOLD ONTO THIS ANVIL FOR ME.

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SURE, BUT WHY?

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GETTING TIRED YET?

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YOU BET.

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BECAUSE YOU HAVEN'T MOVED THE
ANVIL, YOU HAVEN'T DONE ANY WORK.

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DOING WORK AND GETTING TIRED ARE
NOT NECESSARILY THE SAME THING.

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CAN WE PUT THIS THING DOWN?

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OF COURSE.

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NOW, WITH THE SLINGSHOT, I DID THE
WORK WHEN I PULLED ON THE STRAP

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AND MOVED IT BACK ABOUT ONE METER.

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WHEN I LET GO OF THE STRAP, THE
SLINGSHOT DID WORK ON THE TOMATO

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WHEN IT PUSHED IT
FORWARD AND SPED IT UP.

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I LOVED THE SPLAT.

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NOW, WITH THE 25-KILOGRAM
ANVIL, I HAD TO SUPPLY A FORCE

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OF ABOUT 55 POUNDS, GOING
AGAINST GRAVITY AS I PICKED IT UP.

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THE HIGHER I LIFTED THE
ANVIL, THE MORE WORK I DID,

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AND THE MORE GRAVITATIONAL
ENERGY THE ANVIL HAD.

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THEN THE ANVIL MUST
HAVE HAD A LOT OF ENERGY

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BECAUSE IT SURE CRUSHED
THE CANTALOUPE.

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BUT JACOB IS HEAVIER
THAN 55 POUNDS.

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DOES THAT MEAN IT WOULD
TAKE MORE WORK TO LIFT HIM?

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YES, THAT'S RIGHT.

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SINCE WORK IS EQUAL TO
FORCE TIMES DISTANCE,

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INCREASING EITHER THE FORCE OR THE
DISTANCE WILL REQUIRE MORE WORK.

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YOU SAID IT TOOK ENERGY TO DO
WORK, SO WHERE DID THE ENERGY COME

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FROM TO LIFT THE ANVIL?

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THE ENERGY CAME FROM THE
CORNFLAKES THAT I HAD

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FOR BREAKFAST THIS MORNING.

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THE CORN GOT ITS ENERGY
FROM THE SUN.

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IT'S GOING TO TAKE A LOT OF ENERGY
TO LIFT JACOB INTO THE TREE HOUSE.

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I THINK IT'S GOING TO TAKE
ALL OUR ENERGY TO DO THE JOB.

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THANKS, DR. "D."

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YOU'RE WELCOME.

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BYE.

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BYE-BYE.

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WOW.

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EXACTLY 3 1/2 METERS.

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THAT'S HIGHER THAN I THOUGHT.

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MY DAD HAD SOME ROPE THAT
WE CAN USE TO LIFT JACOB.

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GREAT.

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LET'S LOWER IT DOWN.

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MAYBE WE COULD ATTACH IT TO
THE TEST DUMMY DOWN BELOW.

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KSNN IS COMING ON.

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GOOD MORNING, EVERYONE.

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I'M TED TOON.

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OUR TOP STORY: KIDS SCIENCE NEWS
NETWORK IS GETTING A FACELIFT.

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THE NEXT TIME YOU SEE
ME, I'LL BE IN THE NEW

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AND IMPROVED KSNN STUDIO.

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YEAH, OKAY, LET'S
GET HIM OUTTA HERE.

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HEY, STOP THAT.

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CUT IT OUT.

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PUT ME DOWN!

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I'M WITH PATTY O. FURNITURE, THE
STUDIO CONSTRUCTION SUPERVISOR.

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PATTY, WHAT CAN YOU TELL
US ABOUT THE REDESIGN?

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WE'RE TAKING OUT ALL THE OLD STUFF
AND REPLACING IT WITH NEW STUFF,

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I.M. WE'RE GOING TOTALLY
TECHNO HERE.

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WE'LL HAVE THE DIGITAL INTERACTIVE
WEATHER BOARD OVER THERE,

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THE REMOTE SATELLITE-- HEY,
WATCH IT WITH THAT NEWS SKUNK!

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SPORTS SUPER SLOW MOTION
SYSTEM OVER HERE, AND THE NEW--

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CAREFUL WITH THAT DYNAMITE!

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HYPERSPEED WIRE SERVICE
FEEDS IN THAT CORNER.

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WELL, THINGS ARE CERTAINLY
CHANGING AROUND HERE.

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BE SURE TO JOIN PATTY AND THE
KSNN NEWS CREW TO LEARN MORE

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ABOUT OUR JOBS AND WHY WE LOVE
THEM AT THE UPCOMING CAREER DAY.

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UNTIL NEXT TIME, I'M
I.M. LISSNING FOR KSNN.

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THE NEW STUDIO SHOULD BE AWESOME.

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YOU BET.

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IS ANYONE GOING TO CAREER DAY?

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ACTUALLY, I'M WORKING ON A
PRESENTATION FOR CAREER DAY.

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AREN'T YOU A LITTLE YOUNG TO
BE THINKING ABOUT A CAREER?

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YOU'RE NEVER TOO YOUNG
TO DO RESEARCH.

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THAT'S TRUE.

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MY MOM WORKS FOR S.W.E. I'VE ALWAYS
BEEN INTERESTED IN ENGINEERING.

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WHAT'S S.W.E.?

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S.W.E. STANDS FOR THE
SOCIETY OF WOMEN ENGINEERS.

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I DON'T KNOW WHAT I WANT TO BE
WHEN I GROW UP, BUT IT'S IMPORTANT

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TO KNOW WHAT'S OUT THERE.

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YOU'RE RIGHT.

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MAYBE WE CAN HELP YOU
WITH YOUR PRESENTATION.

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DON'T FORGET.

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WE HAVE AN ENGINEERING
PROBLEM OF OUR OWN.

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THAT'S TRUE.

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I'VE BEEN THINKING ABOUT OUR
HYPOTHESIS: WE COULD USE A ROPE

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TO PULL JACOB BACK
INTO THE TREE HOUSE.

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WELL, I BETTER GO ATTACH
THE ROPE TO OUR TEST DUMMY.

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WE WERE WONDERING WHAT ALL
THE SANDBAGS WERE DOING

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AT THE BOTTOM OF THE TREE.

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THEY LOOK HEAVY.

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ARE YOU SURE YOU CAN LIFT THEM?

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IT WEIGHS ABOUT 90 POUNDS.

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WHICH IS ALMOST 41 KILOGRAMS.

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IF WE CAN LIFT IT, JACOB
SHOULD BE NO PROBLEM.

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OKAY, WE'RE ALL SET DOWN BELOW.

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WELL, LET'S GET STARTED.

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ARE YOU READY TO PULL?

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YEP, ON A COUNT OF THREE.

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ONE, TWO, THREE.

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CAN YOU TWO GIVE US A HAND?

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THANKS.

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WOW, IT'S STILL HARD TO PULL.

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ARE YOU SURE THIS IS
ONLY 41 KILOGRAMS?

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THIS...ISN'T WORKING.

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OKAY, LET'S LOWER HIM DOWN.

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THAT DIDN'T WORK LIKE
I THOUGHT IT WOULD.

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WE NEED A NEW HYPOTHESIS.

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YOU'RE RIGHT.

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WE DIDN'T THINK THROUGH
THE PROBLEM VERY CAREFULLY.

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I GUESS WE JUMPED TO A
CONCLUSION TOO QUICKLY.

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WE CAN DO THIS.

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WE JUST NEED TO GET ORGANIZED
AND GET BACK TO THE BASICS.

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THE PROBLEM BOARD.

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OKAY, WHAT DO WE KNOW?

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WE KNOW WE NEED TO GET
JACOB INTO THE TREE HOUSE.

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AND THAT IT'S TOO HARD TO
PULL HIM UP WITH A ROPE.

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DR. "D" TOLD US THAT WORK REQUIRES
FORCE APPLIED OVER A DISTANCE.

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AND THAT TAKES ENERGY.

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SO WHAT DO WE NEED TO KNOW?

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WE NEED TO KNOW AN EASIER WAY TO
GET JACOB UP INTO THE TREE HOUSE.

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RIGHT, THERE MUST BE A
MACHINE THAT COULD HELP.

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LIKE AN ELEVATOR OR A CRANE.

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AN ELEVATOR SOUNDS GREAT.

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I'M NOT SURE WHAT
THE POWER SOURCE IS,

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BUT THEY ARE MADE TO LIFT PEOPLE.

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MAYBE WE COULD BUILD A SMALL
ELEVATOR IN THE TREE HOUSE.

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IF WE FOUND A WAY TO
POWER THE ELEVATOR,

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WE COULD EASILY LIFT JACOB.

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I THINK WE NEED TO LEARN
MORE ABOUT ELEVATORS.

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I'LL CHECK THE INTERNET.

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I'LL SEE IF I HAVE
SOMETHING IN MY BOOK BAG.

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YES, CHECK IT OUT.

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ELISHA GRAVES OTIS INVENTED
THE ELEVATOR IN 1853

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AFTER DEVELOPING A SAFETY
DEVICE FOR A LIFT PLATFORM.

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I DIDN'T KNOW ELEVATORS
WERE THAT OLD.

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GUYS, OTIS ELEVATOR HAS A WEBSITE.

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I WONDER IF IT'S THE SAME OTIS.

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I BET IT IS.

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IT SAYS HERE THAT THEY DESIGN

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AND INSTALL ELEVATORS
ALL AROUND THE WORLD.

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I'LL EMAIL THEM AND
SEE IF THEY CAN HELP.

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WHILE YOU'RE ON THE INTERNET, PRINT
OUT AN EXTRA GET-UP-AND-GO SHEET.

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YOU CAN GO TO THE NASA SCI FILES
WEBSITE TO DO RESEARCH AND PRINT

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OUT YOUR OWN GET-UP-AND-GO SHEET.

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HELLO, WE'RE THE TREE
HOUSE DETECTIVES,

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AND WE NEED TO LEARN
MORE ABOUT ELEVATORS.

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WELL, YOU'VE COME
TO THE RIGHT PLACE.

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I'M EDITH DI FRANCESCO,
VICE PRESIDENT

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OF PRODUCT DEVELOPMENT HERE
AT OTIS ELEVATOR COMPANY.

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WOW, THAT SOUNDS INTERESTING.

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DO YOU ACTUALLY BUILD ELEVATORS?

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HERE AT THE TEST TOWER, WE
TEST ELEVATORS FOR SAFETY

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AND EFFICIENCY, AND I DON'T
PERSONALLY BUILD ELEVATORS,

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ALTHOUGH AS A MECHANICAL ENGINEER,
I'VE WORKED ON ELEVATOR DESIGNS.

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YOU'RE AN ENGINEER?

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I'M DOING A REPORT ON
ENGINEERS FOR CAREER DAY.

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GREAT, I'LL SHOW YOU WHERE WE
DESIGN AND TEST OUR ELEVATORS.

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WE HAVE LOTS OF ENGINEERS
WORKING ON ELEVATOR DESIGN.

[00:11:30.705]
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THIS IS OUR TEST TOWER.

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AFTER WE DESIGN THE ELEVATORS,
WE BRING THEM HERE TO TEST THEM

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TO SEE HOW THEY WILL WORK
WHEN THEY'RE INSTALLED.

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HOW DO ELEVATORS WORK?

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ELEVATORS ARE DRIVEN
BY ELECTRIC MOTORS,

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AND ON THE MOTOR SHAFT IS
A PULLEY CALLED A SHEAVE.

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OVER THE SHEAVE HANG STEEL CABLES.

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IT'S BASICALLY A BOX ON A ROPE.

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ON ONE END OF THE CABLE
IS THE ELEVATOR CAR,

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WHICH CARRIES THE PEOPLE, AND ON
THE OTHER END IS THE COUNTERWEIGHT.

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WHAT'S A COUNTERWEIGHT?

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A COUNTERWEIGHT IS A STEEL
FRAME FULL OF WEIGHTS,

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AND IT BALANCES THE WEIGHT OF THE
ELEVATOR CAR AND THE PEOPLE IN IT

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SO THAT IT TAKES LESS
FORCE TO MOVE THE ELEVATOR.

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HOW DOES IT REDUCE THE
AMOUNT OF FORCE NEEDED?

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THINK OF IT LIKE A BALANCED SCALE.

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THE FORCE NEEDED TO TURN THE
SHEAVE IS RELATED TO THE DIFFERENCE

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BETWEEN THE WEIGHT OF THE
CAR WITH THE PEOPLE IN IT

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AND THE WEIGHT OF
THE COUNTERWEIGHT.

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THE CLOSER THOSE TWO ARE IN WEIGHT,
THE MORE BALANCED THE SYSTEM IS

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AND THE EASIER IT IS
TO TURN THE SHEAVE.

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HOW DOES AN ELEVATOR
GO UP AND DOWN?

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WELL, WHEN THE MOTOR
TURNS, THE SHEAVE ROTATES.

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THE CABLES STAY ON THE
SHEAVE IN THESE GROOVES,

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AND WITH THE FRICTION BETWEEN
THE CABLES AND THE SHEAVE,

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THE CABLES MOVE WITH THE
SHEAVE WHEN IT ROTATES,

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MAKING THE ELEVATOR GO UP AND DOWN.

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IT SOUNDS LIKE FRICTION IS A GOOD
THING TO HAVE IN AN ELEVATOR.

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YES, WE CALL IT TRACTION,
AND IT'S VERY IMPORTANT.

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WE DON'T NEED A VERY BIG
ELEVATOR FOR OUR TREE HOUSE.

[00:12:46.955]
DO ELEVATORS COME
IN DIFFERENT SIZES?

[00:12:49.035]
YES, THEY CAN BE AS
SMALL AS A DUMBWAITER,

[00:12:50.725]
ABOUT 1/2 METER BY 1/2 METER.

[00:12:52.375]
AND HOW BIG CAN AN ELEVATOR BE?

[00:12:54.635]
SOME ELEVATORS ARE
AS BIG AS A TRUCK.

[00:12:56.435]
THEY'RE USED TO CARRY FREIGHT
CONTAINERS AT SEAPORTS.

[00:12:59.295]
BUT A TYPICAL COMMERCIAL ELEVATOR
IS ABOUT A METER BY TWO METERS.

[00:13:02.165]
AND CARRIES 10 OR 12 PEOPLE.

[00:13:04.125]
DESIGNING ELEVATORS
SEEMS LIKE A LOT OF WORK.

[00:13:06.125]
IT SOUNDS LIKE A LOT OF FUN.

[00:13:07.955]
IT HAS ITS UPS AND DOWNS.

[00:13:10.175]
THANKS, MRS. DI FRANCESCO.

[00:13:11.495]
WE'VE LEARNED A LOT
ABOUT ELEVATORS.

[00:13:13.295]
YOU'RE WELCOME.

[00:13:14.035]
AND IF YOU HAVE ANY MORE
QUESTIONS, JUST GIVE ME A CALL.

[00:13:16.375]
BYE.

[00:13:17.015]
BYE.

[00:13:17.635]
BYE.

[00:13:19.625]
WOW, I NEVER KNEW
ELEVATORS WERE SO COOL.

[00:13:22.225]
IF WE'RE GOING TO
BUILD AN ELEVATOR,

[00:13:23.545]
WE'LL NEED AN ELECTRIC
MOTOR, A SHEAVE, A SHAFT,

[00:13:26.315]
A COUNTERWEIGHT, AND
AN ELEVATOR CAR.

[00:13:28.835]
BOY, BUILDING AN ELEVATOR
SOUNDS EXPENSIVE.

[00:13:31.235]
NOT TO MENTION COMPLEX.

[00:13:32.665]
THERE HAS TO BE AN EASIER WAY TO
GET JACOB UP INTO THE TREE HOUSE.

[00:13:36.625]
WHAT ABOUT A RAMP?

[00:13:38.285]
WHAT?

[00:13:38.695]
LIKE A BIKE RAMP?

[00:13:39.835]
LIKE THAT ONE OVER THERE.

[00:13:43.825]
OH, HEY, I JUST GOT AN EMAIL
FROM BIANCA AND ANTHONY.

[00:13:47.295]
THEY SAID THAT THEY SPOKE TO
AN ENGINEER ABOUT ELEVATORS.

[00:13:52.185]
THAT WILL BE GREAT FOR BIANCA'S
CAREER DAY PRESENTATION.

[00:13:55.605]
THEY ALSO SAID THAT AN
ELEVATOR WOULD BE TOO EXPENSIVE

[00:13:58.535]
FOR THE TREE HOUSE AND WE MIGHT
WANT TO THINK ABOUT A RAMP INSTEAD.

[00:14:02.315]
WHAT KIND OF RAMP?

[00:14:03.445]
YOU KNOW, RAMPS THAT MAKE BUILDINGS
MORE ACCESSIBLE TO WHEELCHAIRS.

[00:14:07.635]
"INVESTIGATE USE OF RAMP."

[00:14:10.055]
I HAVE A FRIEND WHO
USES A WHEELCHAIR.

[00:14:14.265]
MAYBE HE CAN TELL US ABOUT
WHAT IT'S LIKE TO USE RAMPS.

[00:14:17.015]
LET'S DIAL HIM UP.

[00:14:18.805]
HI, OUR FRIEND JACOB
JUST BROKE HIS FOOT,

[00:14:22.275]
AND HE'S LEARNING A LITTLE BIT

[00:14:23.055]
ABOUT WHAT IT IS LIKE
TO BE DISABLED.

[00:14:24.395]
OH, THAT'S TOO BAD, BUT AT LEAST
HIS FOOT WILL BE WELL SOON.

[00:14:28.065]
HE REALLY WANTS TO COME
INTO THE TREE HOUSE,

[00:14:29.985]
BUT IT'S NOT WHEELCHAIR ACCESSIBLE.

[00:14:31.665]
HAVE YOU EXPERIENCED THAT?

[00:14:33.715]
YES, A LOT OF PLACES ARE NOT BUILT
TO ACCOMMODATE PEOPLE WHO ARE

[00:14:36.985]
IN WHEELCHAIRS OR HAVE OTHER
DISABILITIES, BUT TODAY,

[00:14:39.865]
PUBLIC PLACES ARE REQUIRED BY
LAW TO BE ACCESSIBLE TO EVERYONE.

[00:14:44.355]
I DIDN'T KNOW THAT THERE WERE
LAWS THAT REQUIRE BUILDINGS

[00:14:47.025]
TO BE ACCESSIBLE TO EVERYONE.

[00:14:49.145]
WHAT CAN YOU DO TO MAKE
BUILDINGS ACCESSIBLE

[00:14:50.745]
TO PEOPLE WITH DISABILITIES?

[00:14:52.205]
WELL, A LOT OF BUILDINGS USE
SIMPLE MACHINES, SUCH AS A RAMP,

[00:14:57.135]
WHICH IS AN INCLINED PLANE.

[00:14:58.845]
SOME USE ELEVATORS, BUT THEY
ARE A LITTLE MORE COMPLEX.

[00:15:02.045]
WE NEED TO KEEP IT SIMPLE.

[00:15:03.625]
WHAT IS A SIMPLE MACHINE?

[00:15:05.775]
A SIMPLE MACHINE IS A DEVICE
THAT MAKES WORK MORE CONVENIENT

[00:15:09.175]
BY CHANGING THE SPEED,
DIRECTION, OR AMOUNT OF FORCE.

[00:15:12.595]
THERE ARE SIX SIMPLE MACHINES:
INCLINED PLANE, LEVERS,

[00:15:16.605]
WHEEL AND AXLE, WEDGE,
PULLEY, AND A SCREW.

[00:15:20.335]
WE WERE THINKING THAT A RAMP MIGHT
BE THE ANSWER TO OUR PROBLEM,

[00:15:23.645]
BUT WE DIDN'T KNOW THAT
THEY WERE SIMPLE MACHINES.

[00:15:26.205]
ARE THERE ANY REQUIREMENTS
FOR RAMPS?

[00:15:28.815]
IF YOU WANT TO BUILD JACOB A
RAMP TO GET INTO THE TREE HOUSE,

[00:15:33.005]
THE RAMP WILL NEED TO BE
BUILT AT A 12 TO 1 RATIO.

[00:15:36.515]
THAT REALLY HELPS.

[00:15:37.465]
IT GIVES US A LOT TO THINK ABOUT.

[00:15:39.205]
SEE YOU LATER.

[00:15:39.635]
I WONDER IF THERE ARE ANY
OTHER SIMPLE MACHINES WE NEED

[00:15:42.395]
TO USE TO SOLVE OUR PROBLEM.

[00:15:44.035]
WE NEED TO DO MORE RESEARCH.

[00:15:46.585]
[00:15:49.415]
SO WHAT'S UP?

[00:15:50.555]
HOW MUCH WORK WILL IT TAKE TO
GET JACOB INTO THE TREE HOUSE?

[00:15:53.325]
HOW WILL ENGINEERING HELP
THE TREE HOUSE DETECTIVES?

[00:15:55.965]
IS THE RAMP THE SOLUTION
TO THE PROBLEM?

[00:15:59.475]
FIND OUT NEXT TIME IN THE
CASE OF THE POWERFUL PULLEYS.

[00:16:02.835]

[00:00:01.309]
BE SURE TO ANSWER THE FOLLOWING
QUESTIONS DURING THE SHOW:

[00:00:04.769]
WHAT IS THE DIFFERENCE BETWEEN
POTENTIAL AND KINETIC ENERGY?

[00:00:09.399]
HOW CAN PULLEYS HELP
LIFT A SPACE SHUTTLE?

[00:00:12.719]
[00:00:14.509]
HOW DOES A PULLEY MAKE
LIFTING OBJECTS EASIER?

[00:00:18.789]
WHEN YOU SEE THIS ICON,
THE ANSWER IS NEAR.

[00:00:21.739]
[00:00:25.909]
WOW, 3.5 METERS IS MUCH
HIGHER THAN I THOUGHT.

[00:00:29.219]
YES, THIS'LL BE SOME
INCLINED PLANE.

[00:00:31.839]
LET'S SEE.

[00:00:32.909]
IF THE INCLINED PLANE
IS 3.5 METERS HIGH,

[00:00:36.009]
AT A 12 TO 1 RATIO,
THAT WOULD BE...

[00:00:39.069]
WITH THE CORRECT SLOPE,
THE INCLINED PLANE WOULD BE

[00:00:48.069]
[00:00:52.259]
ABOUT HERE, 42 METERS.

[00:00:55.749]
IT WOULD HAVE TO BE
A REALLY BIG RAMP.

[00:00:57.579]
I THINK RAMPS ARE DEFINITELY
OUT OF THE QUESTION.

[00:01:00.139]
WELL, THERE ARE OTHER
TYPES OF SIMPLE MACHINES.

[00:01:02.319]
AND WE NEED TO KNOW WHAT
THEY ARE AND HOW THEY WORK.

[00:01:05.939]
[00:01:08.189]
MAYBE WE COULD DO AN INTERNET
SEARCH ON SIMPLE MACHINES.

[00:01:11.199]
WE NEED TO TALK TO MORE ENGINEERS.

[00:01:12.369]
MY MOM TALKED TO SOME
ENGINEERS WITH HER S.W.E. GROUP.

[00:01:15.089]
I'M SURE THEY CAN HELP.

[00:01:16.329]
GREAT.

[00:01:16.719]
LET'S GET TO WORK.

[00:01:18.379]
[00:01:19.879]
OH, WE JUST GOT AN
EMAIL FROM DR. "D."

[00:01:23.639]
IT SAYS HE WANTS TO MEET
US AT THE CIRCUS LATER.

[00:01:26.469]
I WONDER WHAT HE WANTS.

[00:01:28.429]
WHO KNOWS, BUT IT'S
DR. D AND THE CIRCUS.

[00:01:30.679]
YOU KNOW THAT'LL BE FUN.

[00:01:31.589]
I BET HE CAN HELP.

[00:01:33.329]
I'M SURE HE KNOWS ALL
ABOUT SIMPLE MACHINES.

[00:01:35.919]
I'LL GO CHECK ON JACOB AND
LET HIM KNOW HOW WE'RE DOING.

[00:01:44.059]
LOOK.

[00:01:44.479]
DR. D'S BALANCING
UP ON THAT BIG BALL.

[00:01:46.479]
I HOPE HE DOESN'T FALL OFF.

[00:01:47.479]
HI, DR. D. IT LOOKS LIKE
YOU'RE HAVING A GREAT TIME.

[00:01:52.289]
YEAH, I'LL BE RIGHT THERE.

[00:01:58.099]
THERE'S A LOT OF SCIENCE
HERE AT THE CIRCUS CENTER.

[00:02:03.089]
SCIENCE?

[00:02:03.309]
I NEVER KNEW THERE COULD
BE SCIENCE AT A CIRCUS.

[00:02:07.039]
SURE, THERE IS.

[00:02:08.089]
THE CIRCUS IS A GREAT
PLACE TO GET SOME IDEAS

[00:02:10.489]
TO HELP YOU SOLVE YOUR PROBLEM.

[00:02:11.979]
WE'RE PARTICULARLY
INTERESTED IN SIMPLE MACHINES.

[00:02:15.059]
GREAT.

[00:02:16.319]
RIGHT NOW, THEY'RE USING A
TEETER BOARD, WHICH IS A LEVER

[00:02:18.829]
WITH A FULCRUM OR A
ROTATIONAL POINT IN THE MIDDLE.

[00:02:21.699]
HOW DOES IT WORK?

[00:02:22.839]
WELL LET'S WATCH THEM.

[00:02:26.319]
[00:02:30.419]
THAT WAS PRETTY NEAT.

[00:02:36.579]
I NOTICED THAT TWO MEN
JUMPED ON THE BOARD,

[00:02:38.239]
BUT ONLY ONE FLEW INTO THE AIR.

[00:02:40.119]
THOSE TWO MEN THAT JUMPED
ARE CALLED PITCHERS.

[00:02:42.359]
THE ONE THAT FLEW UP IN
THE AIR IS CALLED A FLYER.

[00:02:44.759]
I SHOULD'VE GUESSED THAT ONE.

[00:02:46.739]
AFTER THE PITCHERS JUMP, THEY
HAVE A LOT OF POTENTIAL ENERGY.

[00:02:50.229]
IT LOOKED LIKE THE FLYER
WENT AT LEAST TWICE

[00:02:52.539]
AS HIGH AS THE PITCHERS.

[00:02:54.209]
EXACTLY.

[00:02:55.279]
TWO MEN HAVE THE SAME ENERGY
AS ONE MAN TWICE AS HIGH.

[00:02:58.109]
THE FLYER ALSO HELPS BY
PUSHING OFF THE BOARD.

[00:03:01.729]
SO THE LEVER DIDN'T
CREATE ANY ENERGY.

[00:03:03.669]
THAT'S RIGHT.

[00:03:04.349]
THE LEVER CHANGES THE
DOWNWARD MOTION OF THE PITCHERS

[00:03:06.359]
TO THE UPWARD MOTION OF THE FLYERS.

[00:03:08.629]
CORRECT.

[00:03:09.029]
IT'S NOT MAGIC.

[00:03:10.329]
THE TEETER BOARD JUST
LETS THEM TRANSFER ENERGY

[00:03:12.629]
FROM THE PITCHERS TO THE FLYER.

[00:03:14.879]
HOW WOULD YOU LIKE TO
EXPERIENCE THE FLYING TRAPEZE?

[00:03:18.029]
THAT WOULD BE SO COOL.

[00:03:19.919]
NOW, WHAT DOES THE FLYING
TRAPEZE HAVE TO DO WITH ENERGY?

[00:03:24.229]
WHEN YOU'RE WAY UP THERE
ON THE PLATFORM WAITING,

[00:03:27.329]
YOU HAVE A LOT OF POTENTIAL ENERGY.

[00:03:28.619]
THEN WHEN YOU GRAB THE
TRAPEZE AND SWING DOWN,

[00:03:31.049]
YOU BUILD UP KINETIC ENERGY.

[00:03:31.949]
AND WHEN YOU SWING BACK
AGAIN, YOU LOSE KINETIC ENERGY

[00:03:35.379]
AND PICK UP POTENTIAL ENERGY.

[00:03:37.239]
VERY GOOD.

[00:03:38.309]
SO ENERGY ISN'T BEING TRANSFERRED
LIKE ON THE TEETER BOARD.

[00:03:41.299]
IT'S JUST CHANGING
FROM POTENTIAL ENERGY

[00:03:43.719]
TO KINETIC ENERGY
AND THEN BACK AGAIN.

[00:03:45.909]
LET'S WATCH THE ACROBATS
ON THE AERIAL HOOP.

[00:03:48.199]
THESE GUYS ARE REALLY SOMETHING.

[00:03:50.019]
SOMEONE WILL HAVE TO DO A
LOT OF WORK TO LIFT THE HOOP

[00:03:52.679]
AND THE ACROBAT TOGETHER.

[00:03:55.889]
IT LOOKS REALLY EASY
TO PULL THEM UP.

[00:03:57.669]
WHAT ARE THEY USING WITH THE ROPE?

[00:03:59.219]
IT LOOKS LIKE THEY'RE USING
PULLEYS ATTACHED TO THE ROPE.

[00:04:01.459]
I THINK THIS JUST MIGHT BE THE
THING WE NEED TO PULL JACOB

[00:04:03.749]
UP INTO THE TREE HOUSE.

[00:04:05.229]
THIS IS GREAT.

[00:04:06.059]
WE'RE MAKING SOME REAL PROGRESS.

[00:04:07.439]
THANKS, DR. "D."

[00:04:08.529]
YOU'RE WELCOME.

[00:04:09.519]
LET'S SEE ABOUT TRAPEZE TRAINING.

[00:04:11.979]
[00:04:17.169]
LET'S SUMMARIZE WHAT WE KNOW.

[00:04:18.229]
WE KNOW THAT WORK IS
FORCE TIMES DISTANCE

[00:04:20.089]
AND THAT IT TAKES
ENERGY TO DO WORK.

[00:04:21.809]
WE KNOW THAT LEVERS
CHANGE A DOWNWARD MOTION

[00:04:23.349]
TO AN UPWARD MOTION.

[00:04:24.219]
AND THAT ENERGY CHANGES FROM
POTENTIAL ENERGY TO KINETIC ENERGY.

[00:04:27.439]
AND WE ALSO KNOW THAT PULLEYS
LIFT LARGE OBJECTS MORE EASILY.

[00:04:30.919]
OKAY, SO WHAT DO WE NEED TO KNOW?

[00:04:32.739]
WE NEED TO KNOW MORE ABOUT PULLEYS.

[00:04:34.149]
I'LL BET NASA USES PULLEYS.

[00:04:35.669]
I'LL EMAIL MY MOM AND SEE

[00:04:37.089]
IF SHE FOUND ANY ENGINEERS
THAT WE CAN TALK TO.

[00:04:42.629]
AND DON'T FORGET TO EMAIL ANTHONY
AND TELL HIM WHAT WE'VE LEARNED.

[00:04:49.889]
WE'RE MAKING PROGRESS.

[00:04:50.529]
THAT'S A GREAT IDEA.

[00:04:51.589]
AND WE GOT TO GO BECAUSE WE DON'T
WANT TO MISS OUR TRAPEZE CLASS.

[00:05:00.589]
[00:05:01.489]
HI, GUYS.

[00:05:02.379]
HOW'S THE PROJECT GOING?

[00:05:03.729]
GREAT SO FAR.

[00:05:04.809]
THANKS FOR YOUR EMAIL.

[00:05:05.989]
YOUR MOM IS FRIENDS WITH MRS.
JONES, AN AIRSPACE ENGINEER HERE

[00:05:08.619]
AT NASA LANGLEY RESEARCH CENTER.

[00:05:10.299]
R.J.'S MEETING HER AT
THE GANTRY THIS AFTERNOON

[00:05:12.199]
TO TALK ABOUT PULLEYS.

[00:05:13.469]
THAT'S GREAT.

[00:05:14.029]
HE ALSO SAID NOT TO WORRY.

[00:05:15.949]
HE PLANS ON GETTING
PLENTY OF INFORMATION

[00:05:17.489]
FOR YOUR CAREER DAY PRESENTATION.

[00:05:19.229]
SPEAKING OF CAREER
DAY, KSNN'S COMING ON.

[00:05:22.889]
I'M I.M. LISSNING, LIVE
FROM MY DRESSING ROOM.

[00:05:25.949]
DURING THE CONSTRUCTION, I'LL BE
FILING A SERIES OF SPECIAL REPORTS

[00:05:29.439]
ABOUT HOW I PERSONALLY REDESIGN
AND OVERHAUL MY OWN DRESSING ROOM.

[00:05:33.589]
AND I'M THINKING, "IF THIS
IS AS EASY AS IT LOOKS,

[00:05:36.469]
I MAY JUST CHANGE CAREERS."

[00:05:38.889]
THIS ISN'T FUNNY ANYMORE.

[00:05:40.559]
GET ME DOWN.

[00:05:41.729]
UNTIL NEXT TIME, I'M
I.M. LISSNING FOR KSNN.

[00:05:46.969]
I.M.'S PRESENTATION
SHOULD BE INTERESTING.

[00:05:49.029]
HOW'S YOUR REPORT COMING, BIANCA?

[00:05:50.999]
SO FAR, SO GOOD.

[00:05:52.329]
I'VE RESEARCHED ENGINEERING
IN GENERAL, AND THE ENGINEER

[00:05:54.609]
AT OTIS ELEVATOR WAS VERY HELPFUL.

[00:05:56.779]
IN A WAY, WE'RE ENGINEERS
FOR OUR PULLEY PROJECT.

[00:05:59.289]
RIGHT, BUT WE STILL
HAVE A LONG WAY TO GO.

[00:06:01.639]
HAVE YOU FOUND ANYTHING ON
THE INTERNET ABOUT PULLEYS?

[00:06:04.549]
THERE'S LOTS OF INFORMATION
ON THE NASA WEBSITE.

[00:06:06.859]
IT LOOKS LIKE MISS ENNIX FROM
DRYDEN CAN HELP US WITH PULLEYS.

[00:06:09.459]
LET'S DIAL HER UP.

[00:06:12.989]
HI, I'M KIMBERLY ENNIX, AN
AEROSPACE ENGINEER WORKING HERE

[00:06:17.309]
AT THE PROPULSION AND
PERFORMANCE BRANCH

[00:06:19.429]
AT NASA DRYDEN FLIGHT
RESEARCH CENTER.

[00:06:21.949]
WOW, AN AEROSPACE ENGINEER.

[00:06:24.589]
WHAT DOES AN AEROSPACE ENGINEER DO?

[00:06:26.549]
I DO FLIGHT TEST RESEARCH ON
DIFFERENT TYPES OF PLANES.

[00:06:29.859]
WE ACTUALLY PUT OUR
EXPERIMENTS ON REAL JET ENGINES,

[00:06:33.189]
INSTALL THE ENGINES IN
EXPERIMENTAL PLANES,

[00:06:35.549]
AND THEN WE GO OUT AND FLY THEM.

[00:06:37.329]
THAT SOUNDS REALLY COOL.

[00:06:39.249]
ADD THAT TO THE CAREER LIST.

[00:06:40.929]
WE'RE DOING A PROJECT, AND WE
NEED TO LEARN MORE ABOUT PULLEYS.

[00:06:44.099]
WE SAW ON THE WEBSITE
THAT NASA USES PULLEYS

[00:06:46.079]
TO LIFT THE SPACE SHUTTLE
ONTO THE BACK OF A 747 PLANE.

[00:06:49.719]
HOW CAN PULLEYS HELP
LIFT THE SPACE SHUTTLE?

[00:06:51.609]
WELL, TO LIFT THE SPACE SHUTTLE,

[00:06:53.639]
THEY USE THE MATE/DEMATE
DEVICE KNOWN

[00:06:55.919]
AS THE M.D.D. THE M.D.D.
IS THIS LARGE, GANTRY-LIKE,

[00:07:00.029]
STEEL STRUCTURE, WHERE THE SPACE
SHUTTLE RECEIVES POST-FLIGHT

[00:07:04.389]
SERVICING AND IS PREPARED
FOR THE FERRY FLIGHT BACK

[00:07:07.329]
TO NASA KENNEDY SPACE CENTER.

[00:07:09.459]
THE M.D.D. HAS TWO 100-FOOT TOWERS
THAT ARE CONNECTED AT 80 FEET

[00:07:14.209]
BY A HORIZONTAL STRUCTURE.

[00:07:16.119]
WHAT DOES THE HORIZONTAL
STRUCTURE DO?

[00:07:18.099]
IT CONTROLS AND GUIDES A
LARGE LIFT BEAM THAT ATTACHES

[00:07:21.549]
TO THE SPACE SHUTTLE
TO RAISE OR LOWER IT.

[00:07:24.159]
THERE ARE THREE LARGE HOISTS, OR
PULLEYS, THAT ARE USED TO RAISE

[00:07:27.839]
AND LOWER THE LIFT BEAM.

[00:07:29.469]
THOSE MUST BE SOME BIG PULLEYS.

[00:07:32.069]
YES, THEY ARE.

[00:07:33.409]
THE SHUTTLE CAN WEIGH
UP TO 232,000 POUNDS,

[00:07:36.579]
BUT EACH OF THE THREE PULLEYS HAS
A 100,000-POUND LIFT CAPABILITY.

[00:07:41.339]
OPERATING TOGETHER, THE
TOTAL LIFTING CAPACITY

[00:07:44.179]
OF THE THREE PULLEYS IS 300,000
POUNDS, BUT FOR SAFETY REASONS,

[00:07:49.109]
WE DON'T EXCEED 240,000 POUNDS.

[00:07:52.109]
WOW.

[00:07:53.219]
THAT'S ABOUT 120 TONS.

[00:07:56.209]
YOU'RE GOOD AT MATH.

[00:07:57.879]
THERE ARE ALSO TWO
EQUIPMENT PULLEYS BUILT

[00:07:59.989]
IN TO EACH TOWER AT
THE 60-FOOT LEVEL.

[00:08:02.419]
EACH PULLEY IS CAPABLE
OF LIFTING 10,000 POUNDS.

[00:08:05.839]
SOUNDS LIKE PULLEYS CAN
LIFT A LOT OF WEIGHT

[00:08:07.849]
AND ARE PRETTY IMPORTANT AT NASA.

[00:08:09.409]
WHAT HAPPENS TO THE SPACE
SHUTTLE ONCE IT'S LIFTED?

[00:08:12.569]
WELL, THE SPACE SHUTTLE
IS THEN PLACED

[00:08:14.979]
ON SPECIAL MOUNTS ATOP THE FUSELAGE

[00:08:17.099]
OF THE NASA 747 SHUTTLE
CARRIER AIRCRAFT.

[00:08:20.669]
IT IS THEN FLOWN BACK TO
THE KENNEDY SPACE CENTER.

[00:08:23.869]
THE SPACE SHUTTLE ACTUALLY
GETS A PIGGY-BACK RIDE.

[00:08:26.679]
ABOUT HOW LONG DOES IT TAKE?

[00:08:28.069]
DEPENDING ON THE WEATHER, IT
USUALLY TAKES ONE TO TWO DAYS.

[00:08:31.569]
THANKS, MISS ENNIX.

[00:08:32.469]
YOU'VE BEEN A BIG HELP.

[00:08:33.609]
YOU'RE WELCOME.

[00:08:34.709]
CALL IF YOU NEED ANYTHING
ELSE, AND GOOD LUCK.

[00:08:38.219]
WOW, THAT IS SO COOL.

[00:08:39.599]
I CAN'T BELIEVE THEY LIFT
THE SHUTTLE WITH PULLEYS.

[00:08:42.819]
IF THE PULLEYS CAN
LIFT THE SPACE SHUTTLE,

[00:08:44.459]
I'M SURE THEY COULD LIFT JACOB.

[00:08:45.699]
I TOOK A LOT OF NOTES.

[00:08:46.889]
I'LL ENTER THEM INTO
THE COMPUTER SO JACOB

[00:08:49.219]
AND THE OTHERS CAN CHECK THEM OUT.

[00:08:50.859]
AND WITH R.J.'S NOTES, WE
SHOULD KNOW A LOT ABOUT PULLEYS.

[00:08:53.799]
HI, R.J. BIANCA'S MOM
SAID YOU'D BE COMING BY.

[00:08:58.469]
HOW CAN I HELP YOU?

[00:08:59.449]
WE NEED TO LEARN MORE
ABOUT PULLEYS.

[00:09:01.109]
WHAT EXACTLY IS A PULLEY?

[00:09:02.799]
WELL, A PULLEY IS A SIMPLE MACHINE.

[00:09:04.319]
IT'S MADE FROM A ROPE AND A WHEEL.

[00:09:07.089]
IT MAKES LIFTING OBJECTS EASIER.

[00:09:08.969]
HOW DOES IT DO THAT?

[00:09:10.059]
IT CHANGES THE DIRECTION
OF THE FORCE.

[00:09:12.119]
FOR EXAMPLE, IF YOU'RE LIFTING
A HEAVY OBJECT OFF THE FLOOR,

[00:09:16.009]
USING A PULLEY MOUNTED
TO THE CEILING,

[00:09:18.449]
YOU CAN PULL DOWN THE ROPE
INSTEAD OF PUSHING UP.

[00:09:21.199]
AREN'T YOU USING THE SAME AMOUNT
OF FORCE NEEDED TO LIFT AN OBJECT?

[00:09:24.089]
GOOD QUESTION, YES, YOU
ARE, BUT IT'S EASIER

[00:09:26.669]
TO PULL DOWN THAN TO PUSH UP.

[00:09:28.389]
SO HOW WOULD I REDUCE THE
AMOUNT OF FORCE NEEDED

[00:09:30.359]
TO LIFT A HEAVY OBJECT?

[00:09:31.929]
IF YOU ADD A SECOND PULLEY, AND YOU
SUPPORT THE LOAD WITH TWO ROPES,

[00:09:38.499]
THEN YOU ONLY NEED HALF
OF THE FORCE TO LIFT IT.

[00:09:41.469]
WHAT IF YOU ADD A THIRD PULLEY AND
SUPPORT THE LOAD WITH THREE ROPES?

[00:09:44.609]
IF YOU DIVIDE THE WEIGHT
OF THE OBJECT BY THE NUMBER

[00:09:46.939]
OF ROPES SUPPORTING THE LOAD,
THEN YOU CAN DETERMINE WHAT KIND

[00:09:50.209]
OF FORCE YOU NEED
TO LIFT THE OBJECT.

[00:09:51.949]
AWESOME.

[00:09:52.869]
SO WHAT DO YOU USE PULLEYS FOR HERE
AT NASA LANGLEY RESEARCH CENTER?

[00:09:56.079]
AS AN AEROSPACE ENGINEER,
AND A LEVEL-THREE MANAGER

[00:09:59.279]
OF NASA'S AVIATION SAFETY
PROGRAM, I USE PULLEYS

[00:10:02.529]
IN CRASHWORTHINESS RESEARCH.

[00:10:04.269]
WHAT'S CRASHWORTHINESS?

[00:10:05.829]
CRASHWORTHINESS IS HOW WELL
AN AIRCRAFT PROTECTS OCCUPANTS

[00:10:08.799]
IN A CRASH.

[00:10:09.779]
A TEAM OF ENGINEERS AND I CONDUCT
TESTS AND ANALYSIS ON MATERIALS,

[00:10:14.419]
ON AIRCRAFT STRUCTURES,
AND FULL-SCALE AIRCRAFT.

[00:10:16.529]
WHY IS THAT IMPORTANT?

[00:10:18.289]
IN A REAL CRASH, IT IS VERY
DIFFICULT TO UNDERSTAND THE DAMAGE

[00:10:21.019]
BECAUSE MANY THINGS ARE DESTROYED.

[00:10:22.699]
BY CONDUCTING CONTROLLED
CRASH TESTS,

[00:10:24.589]
WE CAN BETTER UNDERSTAND
WHAT HAPPENS IN A REAL CRASH,

[00:10:27.349]
AND THEN WE CAN DEVELOP
BETTER DESIGNS

[00:10:29.669]
THAT WILL PROTECT THE PASSENGERS.

[00:10:31.879]
YOU CRASH REAL AIRPLANES HERE?

[00:10:33.729]
WE SURE DO, RIGHT
HERE AT THE GANTRY.

[00:10:35.699]
WHAT EXACTLY IS A GANTRY?

[00:10:37.389]
THE GANTRY IS THE IMPACT
DYNAMICS RESEARCH FACILITY

[00:10:39.689]
WHERE WE PERFORM FULL-SCALE
CRASH TESTS.

[00:10:41.809]
IT WAS ALSO USED BY ASTRONAUTS
DURING THE APOLLO MISSIONS

[00:10:44.539]
TO PRACTICE LANDING ON THE MOON.

[00:10:46.319]
THAT'S COOL.

[00:10:47.499]
HOW DO YOU CRASH PLANES?

[00:10:49.059]
A TEST VEHICLE IS SUSPENDED FROM
TWO SWING CABLES, PULLED BACK,

[00:10:52.189]
AND RELEASED TO ALLOW
THE TEST VEHICLE TO SWING

[00:10:54.199]
INTO THE IMPACT SURFACE BELOW.

[00:10:56.099]
THE SWING CABLES ARE
PYROTECHNICALLY SEPARATED

[00:10:58.179]
FROM THE VEHICLE JUST
PRIOR TO THE IMPACT

[00:11:00.289]
SO THAT FREE FLIGHT
CONDITIONS ARE ESTABLISHED.

[00:11:02.719]
AIRPLANES ARE REALLY HEAVY.

[00:11:04.329]
YOU MUST NEED A LOT OF PULLEYS.

[00:11:05.699]
ACTUALLY, WE ONLY USE ONE PULLEY,
BUT IT'S A PRETTY BIG PULLEY.

[00:11:08.799]
HOW MUCH CAN YOU LIFT?

[00:11:10.259]
WE CURRENTLY CAN ONLY
LIFT UP TO 30,000 POUNDS

[00:11:12.609]
BECAUSE THAT'S THE MAXIMUM
CAPACITY OF THE GANTRY'S BRIDGE.

[00:11:15.779]
HOW CAN YOU LIFT 30,000 POUNDS?

[00:11:18.089]
I RUN STEEL ROPE FROM THE
LIFTING DEVICE THROUGH THE PULLEY

[00:11:20.939]
AND THEN ATTACH IT
BACK TO THE BRIDGE.

[00:11:22.639]
THE PULLEY IS ATTACHED
TO THE AIRCRAFT.

[00:11:24.609]
THIS IS CALLED DOUBLE-HITCHING.

[00:11:25.679]
30,000 POUNDS IS A LOT OF WEIGHT.

[00:11:27.529]
YES, IT IS, BUT WE DON'T NEED
30,000 POUNDS OF FORCE TO LIFT IT.

[00:11:30.989]
WITH ONE PULLEY ATTACHED
TO THE AIRCRAFT,

[00:11:32.819]
YOU HAVE TWO ROPES
SUPPORTING THE LOAD.

[00:11:34.669]
THEN YOU ONLY NEED
15,000 POUNDS OF FORCE.

[00:11:38.169]
OUR FRIEND JACOB DOESN'T
WEIGH 30,000 POUNDS,

[00:11:40.469]
SO I BET WE COULD USE PULLEYS TO
LIFT HIM WITH NO PROBLEM AT ALL.

[00:11:43.759]
THANKS, MRS. JONES.

[00:11:44.669]
YOU'RE WELCOME, AND GOOD LUCK,
AND CALL IF YOU NEED ANYTHING.

[00:11:49.529]
OKAY.

[00:11:50.109]
SO WHAT'S UP?

[00:11:50.599]
HOW WILL THE TREE HOUSE DETECTIVES
USE PULLEYS TO LIFT JACOB?

[00:11:54.819]
WILL IT BE SAFE?

[00:11:55.609]
IS THERE A BETTER SOLUTION?

[00:11:57.719]
STAY TUNED FOR THE ANSWERS IN THE
NEXT EXCITING CHAPTER OF THE CASE

[00:12:01.829]
OF THE POWERFUL PULLEYS.

[00:12:03.279]
[00:00:00.122]
LOOK FOR THE ANSWERS TO
THE FOLLOWING QUESTIONS:

[00:00:04.382]
HOW CAN YOU DETERMINE HOW MUCH
MASS IS NEEDED TO LIFT A LOAD?

[00:00:08.202]
[00:00:09.722]
WHAT SHOULD THE TREE
HOUSE DETECTIVES CONSIDER

[00:00:11.632]
TO SAFELY LIFT JACOB?

[00:00:15.022]
WHAT ARE HUMAN FACTORS?

[00:00:17.122]
[00:00:19.562]
WHEN YOU SEE THIS ICON,
THE ANSWER IS NEAR.

[00:00:22.532]
[00:00:24.682]
AND BECAUSE PULLEYS REDUCE
THE AMOUNT OF FORCE NEEDED,

[00:00:27.382]
THEY'RE INEXPENSIVE, EASY
TO SET UP AND OPERATE.

[00:00:30.112]
WE MUST CONSTRUCT A PULLEY SYSTEM.

[00:00:33.322]
A PULLEY SYSTEM IS
DEFINITELY THE WAY TO GO.

[00:00:36.062]
[00:00:37.932]
OKAY, SO WE KNOW WE NEED TO
USE PULLEYS TO LIFT JACOB

[00:00:40.802]
UP INTO THE TREE HOUSE,
BUT HOW MANY DO WE NEED?

[00:00:44.282]
I CHECKED WITH THE NASA
SCI FILES KIDS' CLUB

[00:00:46.322]
FROM RALEIGH, NORTH CAROLINA.

[00:00:47.762]
I'LL SEE IF WE CAN TALK TO THEM.

[00:00:51.772]
DON'T FORGET, WE HAVE TO
DESIGN THE ENTIRE APPARATUS.

[00:00:55.552]
I DON'T KNOW ABOUT AN
APPARATUS, BUT A LIFT CHAIR

[00:00:57.872]
AND A PULLEY SYSTEM SHOULD BE NICE.

[00:00:59.732]
OKAY, FINE, BUT SERIOUSLY,
WE STILL NEED TO DESIGN

[00:01:02.992]
AND BUILD THE LIFT CHAIR.

[00:01:04.492]
AND THE PULLEY SYSTEM.

[00:01:05.922]
RIGHT, BUT WE NEED TO TEST BOTH
BEFORE WE TRY AND LIFT JACOB.

[00:01:09.512]
GUYS, THE SCI FILES
KIDS' CLUB, CHECK IT OUT.

[00:01:13.532]
HI, I'M KATIE IN MRS.
NOWELL'S FOURTH GRADE CLASS

[00:01:16.252]
AT A.B. COMBS ELEMENTARY SCHOOL
IN RALEIGH, NORTH CAROLINA.

[00:01:19.442]
HI, HOW MAY I HELP YOU?

[00:01:21.662]
HI, WE HEARD THAT YOU WERE
WORKING ON AN EXPERIMENT

[00:01:24.342]
TO LEARN MORE ABOUT PULLEYS.

[00:01:25.922]
THAT'S RIGHT.

[00:01:26.422]
WE WANTED TO FIND
OUT HOW PULLEYS WORK.

[00:01:28.072]
CAN YOU TELL US ABOUT
YOUR EXPERIMENT?

[00:01:31.952]
SURE.

[00:01:32.692]
FIRST, EACH GROUP WAS GIVEN A
500-GRAM MASS, TWO DOUBLE PULLEYS,

[00:01:37.692]
A CUP, SOME STRING,
AND SOME PENNIES.

[00:01:41.402]
WE HOOKED THE 500-GRAM
MASS TO THE BOTTOM

[00:01:43.862]
OF THE PULLEY SYSTEM
THAT WE CONSTRUCTED.

[00:01:46.252]
THEIR COMBINED MASS
IS CALLED THE LOAD.

[00:01:47.922]
WHAT DID YOU DO WITH THE PENNIES?

[00:01:49.062]
WE KEPT ADDING PENNIES TO THE
CUP UNTIL THE LOAD WAS LIFTED.

[00:01:53.902]
WE THEN PLACED OUR CUP ON A
BALANCE TO FIND THE TOTAL MASS

[00:01:57.842]
THAT IT TOOK TO LIFT THE LOAD.

[00:01:59.682]
ONCE WE COLLECTED OUR
DATA FROM TWO STRINGS,

[00:02:02.732]
WE REPEATED WITH THREE
AND FOUR STRINGS.

[00:02:05.572]
DID EACH GROUP IN THE
CLASS GET THE SAME DATA?

[00:02:09.052]
NOT EXACTLY, SO WE SHARED OUR
DATA AND TOOK THE CLASS AVERAGE

[00:02:13.082]
OF THE TOTAL MASS THAT
IT TOOK TO LIFT THE LOAD

[00:02:16.072]
FOR EACH NUMBER OF STRINGS.

[00:02:18.432]
WHEN YOU ANALYZED YOUR
DATA, WERE YOU ABLE

[00:02:20.422]
TO COME TO ANY CONCLUSIONS?

[00:02:21.802]
YES, AFTER PUTTING THE CLASS
AVERAGES UP ON THE BOARD,

[00:02:26.102]
IT WAS PRETTY OBVIOUS THAT
THE MORE STRINGS WE USED,

[00:02:28.872]
THE LESS MASS WE NEEDED
TO LIFT THE LOAD.

[00:02:30.582]
HOW DID YOU CALCULATE HOW MUCH
MASS YOU NEEDED FOR EACH STRING?

[00:02:34.682]
WE COUNTED THE NUMBER OF
STRINGS THAT SUPPORTED THE LOAD

[00:02:38.722]
AND DIVIDED THE COMBINED
MASS BY THE STRING COUNT.

[00:02:42.392]
WE SAW RIGHT AWAY THAT
THERE WAS A PROBLEM

[00:02:44.272]
WHEN WE DID OUR FIRST CALCULATION.

[00:02:46.632]
WHAT WAS THE PROBLEM?

[00:02:48.242]
OUR MASS BEING LIFTED
WAS 545 GRAMS.

[00:02:51.502]
WHEN WE HAD ONLY ONE STRING,

[00:02:53.802]
IT SHOULD'VE TAKEN
545 GRAMS TO LIFT IT.

[00:02:57.392]
INSTEAD, IT TOOK AN
AVERAGE OF 571 GRAMS.

[00:03:01.342]
WE ALSO FOUND THE SAME THING IN
EACH OF OUR OTHER CALCULATIONS.

[00:03:05.152]
COULD YOU HAVE COLLECTED
YOUR DATA INCORRECTLY?

[00:03:07.632]
THAT'S WHAT WE THOUGHT AT FIRST.

[00:03:09.292]
OR THAT WE HAD MADE AN
ERROR IN OUR ARITHMETIC.

[00:03:12.112]
OUR TEACHER GAVE US A HINT.

[00:03:13.742]
WE REALIZED THAT THERE WAS
FRICTION ON OUR PULLEY SYSTEM.

[00:03:16.972]
FRICTION SLOWS THINGS DOWN AND
MAKES IT MORE DIFFICULT TO LIFT.

[00:03:21.772]
THAT'S WHY YOU NEEDED MORE
MASS TO LIFT THE LOAD.

[00:03:24.442]
RIGHT.

[00:03:24.752]
WE CONCLUDED THAT YOU CAN FIND
APPROXIMATELY HOW MUCH MASS IS

[00:03:28.692]
NEEDED TO LIFT THE LOAD BY
DIVIDING BY THE NUMBER OF STRINGS,

[00:03:32.702]
BUT YOU DEFINITELY HAVE
TO CONSIDER FRICTION.

[00:03:35.592]
THANKS SO MUCH FOR YOUR HELP.

[00:03:37.092]
WE WON'T FORGET ABOUT FRICTION.

[00:03:39.002]
YOU'RE WELCOME, AND GOOD
LUCK ON YOUR PROJECT.

[00:03:42.032]
I REALLY LIKED THAT EXPERIMENT,
BUT ANOTHER WAY OF LOOKING AT IT IS

[00:03:45.012]
TO SAY THAT THE PULLEY
MULTIPLIES ON A FORCE.

[00:03:47.722]
WHAT?

[00:03:48.442]
LOOK AT IT THIS WAY: IF WE HAVE
A LOAD SUPPORTED BY FOUR STRINGS,

[00:03:51.762]
THE PULLEYS WILL ALLOW US TO
LIFT SOMETHING FOUR TIMES HEAVIER

[00:03:54.252]
THAN THE FORCE WE APPLY.

[00:03:55.822]
OH, I GET IT.

[00:03:57.192]
IF I APPLY 10 POUNDS OF FORCE,
THEN I CAN LIFT 40 POUNDS.

[00:04:01.512]
EXACTLY.

[00:04:02.612]
MISS JONES SAID THAT WE DIVIDE
THE TOTAL WEIGHT BY THE NUMBER

[00:04:05.122]
OF ROPES SUPPORTING THE LOAD.

[00:04:06.582]
THE KIDS' CLUB SHOWED
US HOW TO DO THAT TOO.

[00:04:09.432]
SO IF THE TOTAL WEIGHT IS
120 POUNDS, OR 54 KILOGRAMS,

[00:04:13.912]
AND WE HAD 6 ROPES SUPPORTING THE
LOAD, THEN THAT'S ABOUT 20 POUNDS

[00:04:18.772]
OF PULLING FORCE, AND WITH
FRICTION, MAYBE A LITTLE MORE.

[00:04:21.552]
THAT WOULD TAKE ABOUT...

[00:04:24.982]
SIX PULLEYS.

[00:04:26.132]
WOW, WITH MY 20 POUNDS OF
FORCE, I CAN LIFT 120 POUNDS.

[00:04:33.352]
I'VE MULTIPLIED MY
FORCE BY SIX TIMES.

[00:04:35.212]
THAT'S OUR NEW HYPOTHESIS.

[00:04:37.812]
IF WE USE ROPE, PULLEYS,
AND A LIFT CHAIR,

[00:04:40.692]
WE CAN LIFT JACOB BACK
INTO THE TREE HOUSE.

[00:04:43.962]
BUT WHAT IF I WANTED TO
LIFT JACOB BY MYSELF?

[00:04:46.662]
20 POUNDS STILL SEEMS
LIKE A LOT TO ME.

[00:04:49.382]
MAYBE WE CAN MULTIPLY
OUR FORCE EVEN MORE

[00:04:51.552]
BY ADDING MORE ROPE AND PULLEYS.

[00:04:53.572]
IT LOOKS LIKE WE HAVE
SOME WORK TO DO.

[00:05:09.352]
[00:05:10.622]
OKAY, WE'RE ABOUT READY TO TEST.

[00:05:12.112]
WAIT, WAIT.

[00:05:13.162]
UH, WE HAVE A THREE-PULLEY SYSTEM.

[00:05:15.332]
I WISH WE FOUND SIX PULLEYS.

[00:05:17.022]
DO YOU THINK OUR HYPOTHESIS
WILL STILL WORK?

[00:05:19.672]
IT SHOULD.

[00:05:20.612]
WITH THREE PULLEYS, WE'LL NEED MORE
FORCE, BUT I THINK WE CAN DO IT.

[00:05:24.462]
AND THE TEST WEIGHT IS 120 POUNDS.

[00:05:27.122]
OKAY, R.J., I THINK WE'RE READY.

[00:05:30.112]
READY UP HERE.

[00:05:31.792]
OKAY, WE'RE READY TO GO.

[00:05:33.782]
ACCORDING TO MY CALCULATIONS,
120 POUNDS DIVIDED

[00:05:36.972]
BY THREE SUPPORTING ROPES EQUALS
ABOUT 40 POUNDS OF PULLING FORCE.

[00:05:40.892]
DON'T FORGET FRICTION.

[00:05:42.202]
OKAY, 45.

[00:05:43.542]
BUT WE DEFINITELY
NEED TO PULL TOGETHER.

[00:05:46.142]
OKAY, EVERYBODY READY?

[00:05:47.382]
MM-HMM.

[00:05:48.002]
ONE, TWO, THREE, PULL.

[00:05:51.342]
[00:06:07.952]
WHERE'S JACOB?

[00:06:10.042]
[00:06:11.172]
OOPS.

[00:06:13.282]
TREE HOUSE, WE HAVE A PROBLEM.

[00:06:15.422]
WE NEED TO DO MORE RESEARCH.

[00:06:16.632]
WE NEED TO GO TO THE PROBLEM BOARD.

[00:06:19.372]
YEAH.

[00:06:20.282]
ALL RIGHT, WE KNOW THAT WORK IS
A FORCE APPLIED OVER A DISTANCE.

[00:06:24.822]
AND THAT IT TAKES
ENERGY TO DO WORK.

[00:06:26.912]
WE ALSO KNOW THAT A LEVER CAN
CHANGE THE DIRECTION OF A FORCE,

[00:06:29.822]
AND POTENTIAL AND KINETIC ENERGY
CAN CHANGE BACK AND FORTH.

[00:06:32.742]
AND PULLEYS REDUCE THE AMOUNT OF
FORCE NEEDED TO LIFT AN OBJECT.

[00:06:36.682]
FIRST, WE NEED TO KNOW HOW
TO MAKE THE LIFT CHAIR SAFER.

[00:06:38.992]
AND WE ALSO NEED TO KNOW IF
THERE'S ANYTHING ELSE WE CAN DO

[00:06:41.862]
TO USE LESS ROPE.

[00:06:43.602]
SINCE WE DON'T HAVE ANY MORE
PULLEYS, I THINK WE NEED TO FIND

[00:06:46.092]
OUT IF THERE'S ANOTHER SIMPLE
MACHINE THAT WE CAN USE

[00:06:48.032]
TO MAKE IT EASIER TO LIFT JACOB.

[00:06:50.292]
UNTIL THE TEST DUMMY FELL
OFF, IT WAS DIFFICULT TO PULL.

[00:06:53.342]
WE NEED TO TALK TO
SOMEONE ABOUT SAFETY.

[00:06:55.522]
MY MOM WORKS WITH
SOME SAFETY ENGINEERS

[00:06:57.142]
AT NASA LANGLEY RESEARCH CENTER.

[00:06:58.242]
I'LL EMAIL HER.

[00:06:59.582]
MAYBE SHE CAN HELP US.

[00:07:02.222]
I'LL GO SEE DR. "D."

[00:07:03.532]
MAYBE HE COULD HELP US FIGURE
OUT HOW TO USE LESS ROPE.

[00:07:06.162]
WE'VE STILL GOT SOME WORK

[00:07:06.982]
TO DO BEFORE WE LET THE REAL JACOB
GET ANYWHERE NEAR THE TREE HOUSE.

[00:07:10.652]
GREAT, MY MOM WROTE BACK.

[00:07:12.372]
MISS RINE IS A SAFETY ENGINEER,
AND SHE'S GOING TO MEET

[00:07:14.382]
WITH US THIS AFTERNOON.

[00:07:16.032]
GREAT.

[00:07:16.552]
LET'S GET UP AND GO.

[00:07:18.032]
HI, WE'RE THE TREE
HOUSE DETECTIVES.

[00:07:21.542]
ARE YOU MISS RINE?

[00:07:22.532]
YES, HOW CAN I HELP YOU TODAY?

[00:07:23.882]
WE'RE DESIGNING A LIFT
CHAIR AND A PULLEY SYSTEM,

[00:07:25.582]
TO HELP GET OUR FRIEND WITH A
BROKEN FOOT UP INTO THE TREE HOUSE.

[00:07:28.472]
AND WE WANT TO MAKE SURE
THAT IT IS SAFE TO USE.

[00:07:31.002]
WELL, YOU'VE COME
TO THE RIGHT PLACE.

[00:07:32.252]
I AM A SAFETY ENGINEER HERE AT
NASA LANGLEY RESEARCH CENTER.

[00:07:35.802]
WHAT DOES A SAFETY ENGINEER DO?

[00:07:37.912]
WELL, WE DO LOTS OF THINGS,
LIKE EVALUATING PROJECTS OR JOBS

[00:07:41.002]
TO IDENTIFY POTENTIAL
HAZARDS OR RISKS.

[00:07:43.382]
WE ALSO DEVELOP SAFETY
PLANS AND GUIDELINES

[00:07:46.092]
THAT HELP PREVENT HARMFUL
ACCIDENTS, INCIDENTS, OR MISHAPS.

[00:07:49.512]
WOW, THAT SOUNDS LIKE A COOL
JOB AND LOTS OF RESPONSIBILITY.

[00:07:53.372]
YES, AND WE'RE DOING MORE
THAN DEVELOPING RULES.

[00:07:55.342]
WE'RE ACTUALLY PROTECTING PEOPLE,
PROPERTY, AND THE ENVIRONMENT.

[00:07:58.162]
AND WE NEED TO PROTECT JACOB.

[00:07:59.652]
WHAT ARE SOME THINGS
THAT WE SHOULD CONSIDER?

[00:08:02.622]
HOW MUCH WILL YOU BE LIFTING?

[00:08:04.262]
ABOUT 120 POUNDS.

[00:08:06.292]
YOU'LL NEED TO KNOW IF THERE'S A
LOAD LIMIT ON THE ROPES, PULLEYS,

[00:08:08.782]
OR ANYTHING ELSE YOU WILL BE
USING IN THE LIFTING PROCESS.

[00:08:11.752]
WE HADN'T THOUGHT OF THAT.

[00:08:12.732]
HOW DO YOU FIGURE
OUT THE LOAD LIMIT?

[00:08:14.712]
MOST OF THE TIME, IT'S PRINTED
ON THE PACKAGING OF A PRODUCT.

[00:08:17.472]
IF NOT, LOOK FOR THE MANUFACTURER,
AND CONTACT THEM DIRECTLY.

[00:08:21.392]
WE WILL DEFINITELY DO THAT.

[00:08:23.352]
IS THERE A SAFETY CATCH
ON YOUR PULLEY SYSTEM?

[00:08:25.892]
NO, I DON'T THINK SO.

[00:08:27.842]
A SAFETY CATCH OR
A LOCKING MECHANISM

[00:08:29.362]
OF SOME KIND ARE VERY IMPORTANT

[00:08:30.662]
IN CASE THE PEOPLE PULLING
THE ROPE LOSE THEIR GRIP.

[00:08:33.132]
IT WOULD CATCH AND STOP
THE FALL OF THE CHAIR.

[00:08:35.192]
WE HAVE A LOT TO CHECK OUT.

[00:08:36.692]
AND TO RESEARCH.

[00:08:37.972]
ALSO, MAKE SURE YOUR EQUIPMENT
IS IN GOOD WORKING ORDER.

[00:08:40.652]
YOU DON'T WANT TO USE
WORN OR BROKEN EQUIPMENT.

[00:08:43.182]
AND DON'T FORGET THAT WE HAVE

[00:08:44.262]
TO MAKE SURE THE TREE LIMB IS
STRONG ENOUGH TO SUPPORT JACOB,

[00:08:47.112]
THE LIFT CHAIR, AND
THE PULLEY SYSTEM.

[00:08:48.932]
NOW YOU'RE GETTING IT.

[00:08:50.092]
AND DON'T FORGET ABOUT TESTING YOUR
EQUIPMENT BEFORE YOU LIFT ANYONE.

[00:08:53.642]
WE WILL BE SURE TO TEST EVERYTHING.

[00:08:55.762]
YOU'LL ALSO NEED TO
CONSIDER HUMAN FACTORS.

[00:08:58.142]
WHILE YOU'RE HERE AT THE
CENTER, YOU SHOULD TALK

[00:08:59.782]
TO DR. KARA LATORELLA.

[00:09:01.412]
SHE'S A HUMAN FACTORS ENGINEER.

[00:09:03.312]
GREAT.

[00:09:03.992]
I'LL GIVE HER A CALL AND
LET HER KNOW YOU'RE COMING.

[00:09:05.812]
THANKS.

[00:09:06.642]
YOU'RE WELCOME, AND GOOD
LUCK WITH YOUR PROJECT.

[00:09:09.612]
[00:09:15.402]
OH, HI, CATHERINE.

[00:09:16.532]
LAURA RINE SAID YOU'D
BE STOPPING BY.

[00:09:17.942]
HAVE A SEAT.

[00:09:21.202]
HOW MAY I HELP YOU?

[00:09:22.812]
OUR FRIEND JACOB BROKE HIS FOOT,
AND WE'VE DESIGNED A LIFT CHAIR

[00:09:25.702]
TO HELP HIM TO GET
INTO THE TREE HOUSE.

[00:09:29.532]
MISS RINE GAVE US SOME
GOOD SUGGESTIONS ON HOW

[00:09:31.662]
TO MAKE THE CHAIR
SAFER, BUT SHE SAID

[00:09:33.142]
THAT WE SHOULD ALSO CONSIDER
THE SCIENCE OF HUMAN FACTORS.

[00:09:35.752]
SHE SAID THAT YOU COULD
HELP US WITH HUMAN FACTORS.

[00:09:37.332]
I SURE CAN.

[00:09:38.152]
HUMAN FACTORS IS THE DESIGN OF
THINGS, SPACES, AND PROCESSES

[00:09:41.402]
SO THEY FIT BETTER
WITH PEOPLE IN TERMS

[00:09:43.512]
OF HOW PEOPLE ARE
DESIGNED PHYSICALLY

[00:09:45.342]
AND HOW WE PROCESS INFORMATION.

[00:09:46.342]
WHY IS IT IMPORTANT?

[00:09:48.492]
WELL, WHEN THINGS OR
PROCESSES OR AREAS ARE DESIGNED

[00:09:51.172]
WITHOUT CONSIDERING HUMAN FACTORS,
THEY MAY BE REALLY DIFFICULT

[00:09:54.052]
TO USE, AND SO THEY
MAY NOT BE USED AT ALL.

[00:09:56.302]
SO WHERE DO YOU START?

[00:09:57.532]
WELL, WE START WITH STANDARDS
AND GUIDELINES THAT ARE BASED

[00:09:59.672]
ON SCIENTIFIC PRINCIPLES.

[00:10:01.622]
FOR EXAMPLE, THEY HELP US
UNDERSTAND HOW THE EYE WORKS,

[00:10:04.232]
WHICH WOULD HELP US UNDERSTAND
WHAT COLORS TO USE IN OUR DISPLAYS.

[00:10:07.492]
OH, I GET IT.

[00:10:08.002]
THEN WE USE WHAT WE KNOW IS
GOOD FOR HUMAN OPERATORS,

[00:10:10.772]
AND WE GET REAL OPERATORS
INVOLVED IN THE PROCESS.

[00:10:13.242]
THIS IS CALLED USER CENTER DESIGN.

[00:10:14.882]
WHAT ARE YOU WORKING ON NOW?

[00:10:16.252]
WELL, HERE AT NASA LANGLEY
RESEARCH CENTER, WE DESIGN DISPLAYS

[00:10:18.982]
AND AIDING TECHNOLOGIES
FOR AIRPLANE COCKPITS.

[00:10:21.562]
WE DO USER CENTER DESIGN OF THESE
CONCEPTS BY INVOLVING REAL PILOTS

[00:10:25.252]
AND TESTING THEM IN AIRCRAFT
SIMULATORS LIKE THIS ONE,

[00:10:27.462]
THE I.F.D. WHAT IS THE I.F.D.?

[00:10:29.802]
THE I.F.D. IS INTEGRATION
FLIGHT DECK.

[00:10:32.202]
THE I.F.D. IS A COPY OF THE FLIGHT
DECK ON THE NASA BOEING 757.

[00:10:36.822]
WE LEARNED THAT, IN DESIGNING, YOU
HAVE TO USE THE ITERATIVE PROCESS.

[00:10:40.442]
WHERE YOU TEST, EVALUATE,
AND REDESIGN.

[00:10:41.812]
HUMAN FACTORS IS SORT OF LIKE THAT.

[00:10:43.652]
YES, THAT'S RIGHT.

[00:10:44.412]
THE ITERATIVE DESIGN
PROCESS IS AN IMPORTANT PART

[00:10:46.602]
OF USER CENTER DESIGN.

[00:10:48.032]
YOU WANT TO INVOLVE USERS ALL
THE WAY THROUGH THE PROCESS

[00:10:50.392]
FROM CONCEPT FORMATION ALL
THE WAY THROUGH TO TESTING

[00:10:53.022]
IN A REAL ENVIRONMENT.

[00:10:54.222]
WHAT KIND OF HUMAN FACTORS SHOULD
WE CONSIDER FOR OUR LIFT CHAIR?

[00:10:57.402]
WELL, FIRST, YOU NEED TO
DEFINE YOUR USER POPULATION.

[00:10:59.582]
WILL JACOB BE THE ONLY
ONE USING THE CHAIR,

[00:11:01.262]
OR WILL OTHER FRIENDS
USE IT AS WELL?

[00:11:02.952]
WE HADN'T THOUGHT OF OTHER USERS.

[00:11:05.122]
IT WOULD BE NICE TO HAVE FOR OTHER
PEOPLE WHO MIGHT NEED TO BE LIFTED.

[00:11:08.512]
WELL, YOU NEED TO CONSIDER
YOUR USER'S REQUIREMENTS,

[00:11:10.512]
THE DESIGN GOALS TOO.

[00:11:12.172]
SO THEY MAY BE SAFETY,
COMFORT, USABILITY.

[00:11:15.312]
ANYTHING ELSE?

[00:11:16.372]
YOU NEED TO CONSIDER THE
ANTHROPOMETRIC CHARACTERISTICS

[00:11:18.692]
OF YOUR USERS.

[00:11:19.852]
ANTHROPOMETRIC?

[00:11:21.052]
WHAT IS THAT?

[00:11:21.912]
ANTHROPOMETRY IS THE
STUDY OF MEASURING PEOPLE,

[00:11:24.622]
THEIR STATIC MEASUREMENTS,
SUCH AS ARM LENGTH AND HEIGHT,

[00:11:27.812]
AND THEN THERE'S FUNCTIONAL
MEASUREMENTS,

[00:11:29.272]
SUCH AS FEELING, ANGLE, AND REACH.

[00:11:31.122]
WOW, WE HAVE A LOT TO CONSIDER.

[00:11:33.712]
THANKS, DR. LATORELLA.

[00:11:35.392]
OH, YOU'RE WELCOME.

[00:11:36.372]
LET ME KNOW HOW YOUR
CHAIR WORKS OUT.

[00:11:38.642]
[00:11:40.622]
HI, GUYS.

[00:11:41.182]
HI, DR. "D."

[00:11:41.862]
WHAT HAVE YOU BEEN DOING?

[00:11:42.772]
JUST WENT FOR A BIKE RIDE
TO GET A LITTLE EXERCISE.

[00:11:45.552]
HOW'S YOUR PROJECT COMING?

[00:11:46.812]
WE'RE EXCITED ABOUT USING PULLEYS
TO LIFT JACOB INTO THE TREE HOUSE.

[00:11:49.882]
BUT WE ENDED UP WITH
A LOT OF EXCESS ROPE.

[00:11:52.412]
ARE WE DOING SOMETHING WRONG?

[00:11:54.112]
I FIGURED YOU'D HAVE SOME
QUESTIONS ABOUT PULLEYS,

[00:11:56.852]
SO I SET UP A MODEL OVER HERE.

[00:11:58.262]
LET'S TRY IT OUT.

[00:11:59.742]
I HAVE FOUR KILOGRAMS OR
ABOUT NINE POUNDS ATTACHED

[00:12:06.292]
TO THIS PULLEY SYSTEM.

[00:12:07.762]
GO AHEAD AND PULL ON THE STRING.

[00:12:13.262]
THAT'S REALLY EASY.

[00:12:14.692]
WHY DON'T YOU LIFT THE WEIGHT,
WHICH WE CALL THE LOAD, ONE METER?

[00:12:17.492]
WE'LL CALL THIS THE LOAD DISTANCE.

[00:12:20.352]
WAIT A MINUTE, ANTHONY.

[00:12:29.352]
[00:12:34.652]
WHERE DID ALL THIS
STRING COME FROM?

[00:12:36.962]
I DON'T KNOW.

[00:12:38.362]
WHAT'S WRONG?

[00:12:39.282]
NOTHING'S WRONG.

[00:12:40.172]
LET ME EXPLAIN.

[00:12:41.322]
SIMPLE MACHINES ALLOW YOU
TO MULTIPLY YOUR FORCE.

[00:12:44.222]
IN THIS CASE, YOU LIFT AN OBJECT
EIGHT TIMES AS HEAVY AS YOUR FORCE.

[00:12:48.282]
RIGHT, WE LEARNED FROM
THE SCI FILES KIDS' CLUB

[00:12:50.682]
THAT YOU COUNT THE NUMBER OF
STRINGS SUPPORTING THE LOAD.

[00:12:53.412]
[00:12:55.392]
I COUNT EIGHT STRINGS, AND THAT'S
WHY WE CAN MULTIPLY OUR FORCE

[00:12:57.882]
EIGHT TIMES.

[00:12:58.892]
VERY GOOD, BUT THERE
IS A TRADE OFF.

[00:13:00.072]
WHAT DO YOU MEAN?

[00:13:01.872]
REMEMBER THAT WORK IS EQUAL
TO FORCE TIMES DISTANCE.

[00:13:06.542]
OKAY.

[00:13:07.082]
WITH SIMPLE MACHINES LIKE PULLEYS,

[00:13:09.662]
YOU CAN MULTIPLY YOUR
FORCE, BUT NOT THE WORK.

[00:13:12.732]
SO IN THIS CASE, YOU'VE
MULTIPLIED YOUR FORCE EIGHT TIMES,

[00:13:15.882]
BUT HOW MUCH STRING DID
YOU HAVE TO PULL IN?

[00:13:20.412]
WE'LL CALL THIS YOUR DISTANCE.

[00:13:22.722]
EIGHT METERS.

[00:13:27.642]
THAT MEANS OUR DISTANCE IS
EIGHT TIMES THE LOAD DISTANCE.

[00:13:30.852]
DOES IT ALWAYS WORK THAT WAY?

[00:13:32.172]
YES, IT DOES.

[00:13:33.752]
IF YOU MULTIPLY YOUR
FORCE, THE TRADE OFF IS

[00:13:37.182]
THAT YOUR DISTANCE WILL ALWAYS BE
GREATER THAN THE LOAD DISTANCE.

[00:13:41.222]
TAKE A LEVER FOR EXAMPLE.

[00:13:43.262]
[00:13:52.612]
WHY DON'T I STAND OVER HERE
AND HAVE YOU TRY TO LIFT ME

[00:13:55.762]
UP BY PUSHING OVER THERE?

[00:13:58.382]
TRY IT WITH JUST ONE HAND.

[00:14:00.222]
OKAY.

[00:14:02.212]
I CAN'T BELIEVE I JUST DID THAT.

[00:14:10.092]
THAT WAS EASY.

[00:14:12.172]
WELL, IF YOUR FORCE IS FIVE
TIMES FURTHER FROM THE FULCRUM

[00:14:14.972]
OR ROTATIONAL POINT THAN THE LOAD,

[00:14:17.102]
YOU'LL MULTIPLY YOUR
FORCE BY FIVE TIMES.

[00:14:20.482]
BUT YOUR DISTANCE--
HOW FAR YOU PUSH DOWN--

[00:14:22.972]
WILL ALSO BE FIVE TIMES GREATER

[00:14:24.942]
THAN THE LOAD DISTANCE--
HOW FAR I MOVE UP.

[00:14:30.182]
THIS IS REALLY COOL.

[00:14:35.322]
SO IF SIMPLE MACHINES DON'T
ALLOW US TO DO LESS WORK

[00:14:38.372]
OR NEED LESS ENERGY,
WHY DO WE USE THEM?

[00:14:41.532]
I GUESS IT'S BECAUSE THEY
MAKE THE WORK EASIER.

[00:14:43.732]
EXCELLENT.

[00:14:44.482]
WE STILL NEED TO MAKE
OUR WORK EASIER.

[00:14:46.632]
RIGHT NOW, WE'VE MULTIPLIED
OUR FORCE THREE TIMES

[00:14:48.612]
BY USING THREE PULLEYS,
BUT THAT ISN'T ENOUGH

[00:14:51.022]
TO EASILY LIFT THE
LOAD OF 120 POUNDS.

[00:14:53.632]
BUT IF WE ADD MORE PULLEYS TO
MULTIPLY THE FORCE EVEN MORE,

[00:14:56.652]
THAT MEANS THAT WE HAVE TO
PULL IN A LOT MORE ROPE.

[00:14:58.942]
WOW, MAYBE WE NEED TO USE A
DIFFERENT KIND OF SIMPLE MACHINE.

[00:15:01.732]
DON'T SCRAP YOUR PULLEY IDEA.

[00:15:03.752]
YOU MIGHT WANT TO CONSIDER
COMBINING OTHER SIMPLE MACHINES

[00:15:06.122]
WITH YOUR PULLEY SYSTEM.

[00:15:07.342]
YOU MEAN LIKE, USE A LEVER
WITH OUR PULLEY SYSTEM?

[00:15:09.762]
THAT'S A POSSIBILITY.

[00:15:11.132]
ANOTHER ONE IS A WHEEL AND AXLE.

[00:15:13.102]
TAKE MY BIKE FOR EXAMPLE.

[00:15:14.452]
THIS COULD ALSO BE
CALLED A CRANK AND AXLE.

[00:15:19.602]
THIS WHEEL WITH THE CHAIN
ATTACHED IS THE AXLE.

[00:15:21.872]
IT'S ATTACHED TO THIS
CRANK WITH THE PEDAL.

[00:15:24.842]
TO FIND OUT HOW THIS
MACHINE MULTIPLIES THE FORCE,

[00:15:27.672]
ALL WE HAVE TO DO IS, DIVIDE
THE RADIUS OF THE CRANK

[00:15:30.662]
BY THE RADIUS OF THE AXLE.

[00:15:32.622]
R.J., WOULD YOU MAKE THE
MEASUREMENTS, PLEASE?

[00:15:35.002]
[00:15:37.462]
THE CRANK IS 16 CENTIMETERS,
AND THE AXLE IS 8 CENTIMETERS,

[00:15:46.462]
[00:15:47.052]
SO THAT MEANS THE MACHINE
MULTIPLIES THE FORCE BY 2.

[00:15:50.302]
THAT'S GREAT.

[00:15:50.592]
ANOTHER POSSIBILITY YOU MAY
WANT TO EXPLORE IS GEARS.

[00:15:53.852]
I'M GOING TO VISIT MY
GRANDPARENTS IN SAN DIEGO.

[00:15:59.122]
WE'RE PLANNING ON
GOING TO LEGOLAND.

[00:16:01.052]
I BET THERE ARE A LOT
OF GEARS IN LEGOLAND.

[00:16:03.102]
I'LL SEND THEM AN EMAIL
AND SEE IF I CAN SPEAK

[00:16:04.762]
WITH SOMEONE ABOUT GEARS.

[00:16:05.952]
GREAT.

[00:16:07.142]
BYE, DR. D. THANKS.

[00:16:08.532]
BYE.

[00:16:10.712]
SO WHAT'S UP?

[00:16:11.982]
WILL THE TREE HOUSE DETECTIVES BE
ABLE TO MAKE THE LIFT CHAIR SAFE?

[00:16:15.362]
HOW WILL HUMAN FACTORS CHANGE
THE DESIGN OF THE LIFT CHAIR?

[00:16:18.412]
WHAT OTHER SIMPLE MACHINES CAN
THE TREE HOUSE DETECTIVES USE

[00:16:20.892]
TO HELP THEM LIFT JACOB?

[00:16:22.212]
FIND OUT IN THE CONCLUSION OF
THE CASE OF THE POWERFUL PULLEYS.

[00:16:25.682]
[00:00:01.139]
ANSWER THESE FINAL QUESTIONS,
AND HELP SOLVE THE CASE

[00:00:03.609]
OF THE POWERFUL PULLEYS.

[00:00:05.249]
HOW DOES A GEAR WORK?

[00:00:07.279]
HOW DOES A BELAY MAKE
THE LIFT CHAIR SAFER?

[00:00:12.379]
HOW DOES A WENCH HELP
SOLVE THE PROBLEM?

[00:00:15.229]
[00:00:16.289]
WHEN YOU SEE THIS ICON,
THE ANSWER IS NEAR.

[00:00:21.079]
[MUSIC]

[00:00:30.079]
[00:00:46.679]
HELLO, MRS. SEVELL.

[00:00:47.689]
HI, YOU MUST BE ONE OF
THE TREE HOUSE DETECTIVES.

[00:00:50.639]
I UNDERSTAND YOU NEED
TO LEARN ABOUT GEARS.

[00:00:53.189]
WE SURE DO.

[00:00:54.209]
WHAT EXACTLY IS A GEAR?

[00:00:55.969]
A GEAR IS ONE OF THE OLDEST
SIMPLE MACHINES INVENTED.

[00:01:00.249]
IN FACT, IT'S A WHEEL AND
AN AXLE, BUT WITH TEETH.

[00:01:03.689]
TEETH?

[00:01:04.219]
WHAT KIND OF TEETH?

[00:01:05.989]
I'LL USE THESE LEGO
GEARS TO SHOW YOU.

[00:01:09.019]
THAT'S COOL.

[00:01:10.559]
GEARS WORK WHEN THE
TEETH OF ONE GEAR MESH

[00:01:16.689]
WITH THE TEETH OF ANOTHER.

[00:01:19.219]
THE FIRST GEAR IS CALLED THE
DRIVER OR THE PRIMARY GEAR.

[00:01:23.349]
NOTICE WHEN I TURN IT, THE NEXT
GEAR, OR THE FOLLOWER GEAR,

[00:01:28.149]
ROTATES IN THE OPPOSITE DIRECTION
BUT AT THE SAME ROTATIONAL SPEED.

[00:01:33.349]
WHAT HAPPENS WHEN YOU PUT TWO GEARS
TOGETHER THAT AREN'T THE SAME SIZE?

[00:01:36.509]
LET'S SEE.

[00:01:37.829]
NOTICE THAT THE FOLLOWER GEAR IS
TWO TIMES LARGER AND HAS TWICE

[00:01:41.599]
AS MANY TEETH AS THE DRIVING GEAR.

[00:01:44.259]
GIVE IT A TRY.

[00:01:45.989]
[00:01:47.029]
THE FOLLOWER ONLY ROTATES
HALF AS MUCH AS THE DRIVER.

[00:01:52.169]
THAT'S RIGHT.

[00:01:52.759]
IT HAS HALF THE ROTATIONAL
SPEED OF THE DRIVER.

[00:01:56.319]
CHANGING ROTATIONAL SPEED IS
ONE OF THE REASONS WE USE GEARS.

[00:02:00.389]
ANOTHER REASON IS TO
MULTIPLY THE FORCE

[00:02:03.639]
ON THE AXLE OF THE FOLLOWER GEAR.

[00:02:06.619]
WE DEFINITELY NEED MORE FORCE,

[00:02:08.109]
BUT HOW DO YOU USE
GEARS TO MULTIPLY FORCE?

[00:02:10.469]
IT'S SIMPLE.

[00:02:12.149]
IF YOU DOUBLE THE SIZE
OF THE FOLLOWER GEAR,

[00:02:14.919]
THE FORCE ON THE AXLE IS
TWICE WHAT IT USED TO BE.

[00:02:17.989]
IS IT ALWAYS THAT EASY?

[00:02:19.719]
YOU CAN ACTUALLY CALCULATE
THE INCREASE IN FORCE

[00:02:22.439]
BY SIMPLY DIVIDING THE NUMBER
OF TEETH ON THE FOLLOWER

[00:02:26.569]
WITH THE NUMBER OF
TEETH ON THE DRIVER.

[00:02:28.839]
SO IN THIS CASE, THE FOLLOWER HAS
40 TEETH, AND THE DRIVER HAS 24.

[00:02:32.889]
40 DIVIDED BY 24 IS...

[00:02:35.859]
ABOUT 1.7.

[00:02:37.299]
THAT MEANS THAT THE FORCE IS
MULTIPLIED ABOUT TWO TIMES.

[00:02:40.219]
THAT'S RIGHT.

[00:02:41.239]
YOU'RE REALLY GOOD WITH NUMBERS.

[00:02:42.799]
WHAT IF THERE ARE THREE GEARS?

[00:02:44.399]
LET'S TRY IT.

[00:02:46.949]
HERE WE HAVE A DRIVER WITH 8
TEETH, A FOLLOWER WITH 24 TEETH,

[00:02:52.579]
AND ANOTHER FOLLOWER WITH 40 TEETH.

[00:02:55.429]
IT LOOKS LIKE THE DRIVER
GEAR GOES AROUND FIVE TIMES

[00:03:00.669]
FOR EVERY ONE TIME THAT THE
LARGEST FOLLOWER GEAR GOES AROUND.

[00:03:03.459]
GOOD OBSERVATION.

[00:03:05.349]
TO FIND THE FORCE MULTIPLIER, YOU
DIVIDE THE 40 TEETH OF THE FOLLOWER

[00:03:10.149]
BY THE 8 TEETH OF THE DRIVER.

[00:03:12.449]
THAT WOULD BE 5.

[00:03:13.729]
BUT WHAT ABOUT THE MIDDLE GEAR?

[00:03:15.349]
THE MIDDLE GEAR DOESN'T MAKE A
DIFFERENCE, EXCEPT FOR THE FACT

[00:03:18.159]
THAT IT CHANGES THE
DIRECTION OF ROTATION.

[00:03:20.609]
LET'S VERIFY OUR RESULTS TO SEE

[00:03:22.279]
IF THE FORCE IS REALLY
MULTIPLIED BY FIVE.

[00:03:25.669]
I'LL PLACE FIVE BRICKS
ON THIS LEVER ARM

[00:03:28.939]
AND PLACE ONE BRICK
THE SAME DISTANCE

[00:03:31.609]
OUT ON THE LEVER ARM
ON THE DRIVER GEAR.

[00:03:34.109]
IT BALANCES, SO WE WERE CORRECT.

[00:03:36.829]
WE'VE MULTIPLIED THE FORCE BY FIVE,

[00:03:38.909]
BUT THAT FOLLOWER DOESN'T
MOVE VERY MUCH AT ALL.

[00:03:40.819]
IT'S JUST LIKE A PULLEY SYSTEM.

[00:03:42.179]
WHENEVER YOU MULTIPLY THE FORCE,
YOU HAVE TO PULL IN A LOT OF ROPE

[00:03:44.579]
TO MOVE THE LOAD A SHORT DISTANCE.

[00:03:46.249]
RIGHT, WHENEVER YOU
USE SIMPLE MACHINES,

[00:03:48.579]
THERE'S ALWAYS A TRADE OFF.

[00:03:50.379]
DR. D SAID THE SAME THING.

[00:03:52.649]
HE ALSO SAID THAT YOU COULD
COMBINE SIMPLE MACHINES IN ORDER

[00:03:55.169]
TO GET A GREATER MULTIPLICATION
OF FORCE.

[00:03:58.329]
CHECK OUT THIS BICYCLE,
FOR EXAMPLE.

[00:04:01.029]
THE CRANK WORKS AS A LEVER.

[00:04:03.049]
WE HAVE A GEAR SYSTEM.

[00:04:04.979]
IN THIS GEAR SYSTEM, THE TEETH
DON'T MESH TOGETHER DIRECTLY.

[00:04:08.699]
THEY ARE CONNECTED BY A CHAIN.

[00:04:11.529]
A BICYCLE USES A LOT
OF SIMPLE MACHINES.

[00:04:13.879]
WHEN YOU HAVE MORE THAN ONE
SIMPLE MACHINE WORKING TOGETHER,

[00:04:17.549]
LIKE ON THE BICYCLE, IT'S
CALLED A COMPOUND MACHINE.

[00:04:21.369]
HERE'S ANOTHER EXAMPLE.

[00:04:23.819]
THIS CRANE IS A COMBINATION
OF A CRANK, OR LEVER,

[00:04:28.189]
ATTACHED TO A GEAR,
CONNECTED TO PULLEYS.

[00:04:32.599]
THIS IS REALLY COOL.

[00:04:34.809]
I'LL BET THAT THIS HELPS
US SOLVE OUR PROBLEM.

[00:04:37.279]
THANKS A LOT, MRS. SEVELL.

[00:04:39.449]
YOU'RE WELCOME.

[00:04:42.349]
[00:04:44.509]
I THINK THIS IS OUR NEW HYPOTHESIS.

[00:04:45.829]
IF YOU USE ROPE, PULLEYS,
GEARS, AND A LIFT CHAIR,

[00:04:49.299]
THEN WE'LL BE ABLE TO LIFT
JACOB INTO THE TREE HOUSE.

[00:04:55.009]
OKAY, WE CAN SECURE JACOB OR
ANYONE ELSE IN THE LIFT CHAIR

[00:04:57.839]
BY USING THIS ROPE AND HARNESS.

[00:04:58.999]
YES, AND THE HANDLES
MAKE IT SAFER TOO.

[00:05:01.189]
AS LONG AS THE LIFT CHAIR CAN
SUPPORT THE HEAVIEST PASSENGER,

[00:05:03.989]
THEN WE'RE IN GOOD SHAPE.

[00:05:05.449]
RIGHT, NOW, ALL WE HAVE
TO FIGURE OUT IS HOW

[00:05:07.099]
TO MAKE THE PULLEY SYSTEM EASY
ENOUGH FOR EVERYONE TO USE.

[00:05:09.459]
LET'S GO AND SEE IF
ANTHONY SENT US AN EMAIL.

[00:05:11.149]
ANTHONY SAID THAT HE LEARNED
A LOT AT LEGOLAND ABOUT GEARS

[00:05:16.899]
AND COMBINING SIMPLE
MACHINES TOGETHER.

[00:05:19.409]
HE SAID THAT HE REMEMBERS SEEING
A LOT OF THINGS IN HIS GARAGE.

[00:05:22.069]
HE THINKS IT MIGHT BE A
GOOD IDEA TO USE GEARS

[00:05:23.899]
WITH OUR PULLEY SYSTEM.

[00:05:25.219]
HE WANTS US TO CHECK WITH
HIS DAD ABOUT USING IT.

[00:05:27.449]
I WONDER WHAT HAS GEARS IN IT.

[00:05:29.219]
WE'LL HAVE TO CHECK THIS OUT.

[00:05:30.909]
OH, DR. D WROTE US AN EMAIL.

[00:05:33.229]
HE SAID THAT IF WE'RE CONCERNED
ABOUT SAFETY, WE SHOULD TALK

[00:05:35.539]
TO HIS CLIMBER FRIEND.

[00:05:36.909]
GREAT, WHILE YOU'RE
ON THE INTERNET,

[00:05:38.469]
PRINT OUT A GET-UP-AND-GO SHEET.

[00:05:39.799]
YOU CAN PRINT OUT YOUR OWN
GET-UP-AND-GO SHEET BY GOING

[00:05:42.719]
TO THE NASA SCI FILES
WEBSITE RESEARCH RACK.

[00:05:49.589]
HI.

[00:05:50.409]
ARE YOU MR. HARDING?

[00:05:52.089]
YES, THAT'S RIGHT.

[00:05:52.919]
YOU MUST BE ONE OF THE
TREE HOUSE DETECTIVES.

[00:05:54.749]
DR. D TELLS ME YOU NEED TO
LEARN MORE ABOUT SAFETY.

[00:05:57.529]
THAT'S RIGHT.

[00:05:58.769]
DR. D MENTIONED THAT
YOU ROCK CLIMB.

[00:06:00.709]
WE WERE WONDERING
HOW YOU MAKE IT SAFE.

[00:06:02.579]
WELL, I CAN SHOW YOU THAT
RIGHT HERE, BUT FIRST,

[00:06:04.239]
WE NEED TO OUTFIT YOU
WITH A CLIMBING HARNESS

[00:06:05.999]
TO TIE THE ROPE IN TO YOU.

[00:06:08.889]
YOU AREN'T GOING TO
PULL ME UP, ARE YOU?

[00:06:10.289]
NO, YOU'RE GOING TO HAVE TO
DO THE CLIMBING YOURSELF.

[00:06:12.849]
THE ROPE IS JUST SIMPLY
THERE TO KEEP YOU SAFE.

[00:06:15.499]
HOW DOES THAT WORK?

[00:06:16.269]
IT'S CALLED BELAYING.

[00:06:18.079]
I TIE ONE END OF THE ROPE INTO
YOUR HARNESS, AND THEN IT GOES

[00:06:21.789]
THROUGH THE EYE BOLT AT THE TOP
AND THEN DOWN TO ME, THE BELAYER.

[00:06:24.909]
IT PASSES THROUGH THIS BELAY DEVICE
CALLED AN A.T.C. OR FIGURE EIGHT.

[00:06:29.519]
IF YOU SLIP AND BEGIN TO FALL, I
SIMPLY PULL ON THE ROPE LIKE THIS,

[00:06:32.689]
AND THE FRICTION WITH THE
A.T.C. STOPS THE ROPE.

[00:06:35.559]
ARE YOU SURE THIS IS GOING TO WORK?

[00:06:37.389]
LET ME SHOW YOU.

[00:06:39.799]
CLIMB UP A FEW FEET,
AND THEN LET GO.

[00:06:42.439]
[00:06:47.669]
OKAY.

[00:06:49.229]
[00:06:53.089]
WOW, IT STOPPED ME