Choose the sheet for the learner's age. Each prints on a single page. Build the project first, then fill it in together.
Ages 5-7: Draw & tell
Name: ______________________Date: ____________
Homemade Science with Bruce Yeany · Pulley Power · Ages 5-7
Pulley Power
Lift the jug with one pulley, then two.
1. Guess first: with two pulleys, will lifting the jug be easier or harder?
◯ Easier◯ Harder◯ The same
2. Draw your broomstick, your pulley, the cord and the jug. Draw an arrow showing which way you pull.
3. With one pulley, which way did the jug go when you pulled down?
◯ Up◯ Down
4. Which was easier to pull?
◯ One pulley◯ Two pulleys
5. With two pulleys, did you pull a short piece of cord or a long piece?
◯ Short◯ Long
Ages 8-10: Predict, test & record
Name: ______________________Date: ____________
Homemade Science with Bruce Yeany · Pulley Power · Ages 8-10
Trading Force for Distance
Predict, measure the pull, and measure the cord.
1. Predict: the jug weighs ______. With a moving pulley, I think the scale will read about ______ because ______.
2. Lift the jug 6 inches (15 cm) each time.
Set-up
Scale reading
Cord pulled
3. With one fixed pulley, the scale read about...
◯ Half the jug's weight◯ The same as the jug's weight◯ Twice the jug's weight
4. What did you find out when you added the moving pulley?
5. Why do you think you had to pull more cord with two pulleys?
Ages 11-14: Explain & design your own test
Name: ______________________Date: ____________
Homemade Science with Bruce Yeany · Pulley Power · Ages 11-14
Mechanical Advantage and Work
Measure mechanical advantage, then check whether the pulleys save work.
1. Record each set-up. Lift height stays 6 in (15 cm).
Set-up
Strands holding jug
Effort force
Cord pulled
Measured MA (load / effort)
2. Using the words force and distance, explain why the moving pulley makes the jug easier to lift.
3. Ideal mechanical advantage = number of supporting strands. Is your measured MA higher or lower than ideal? Give two reasons.
4. Work = force x distance. Calculate work in (effort x cord pulled) and work out (jug weight x lift height) for the two-pulley set-up. Which is bigger?
5. Plan a fair test comparing spool pulleys with store pulleys. What will you change, what will you measure, and what will you keep the same?
6. Where else are pulleys used to lift heavy things? Name one and say how many strands it might use.
Answer guide for grown-ups
Homemade Science with Bruce Yeany · Pulley Power · Answer guide
Answer guide
Ages 5-7: Pulley Power
Any guess is fine; it gets tested next. (Result: easier.)
Open answer: look for effort and careful observation.
Up
Two pulleys
Long
Ages 8-10: Trading Force for Distance
Any prediction is fine. (Result: about half the jug's weight, usually a bit more because of friction.)
Open answer: look for effort and careful observation.
The same as the jug's weight (a little more because of friction).
The pull was only about half as hard, but I had to pull about twice as much cord (about 12 inches for a 6-inch lift).
Two strands hold the jug, and both have to get shorter when it rises, so you pull twice the cord. You trade force for distance.
Ages 11-14: Mechanical Advantage and Work
Open answer: look for effort and careful observation.
The jug hangs on two strands, so each carries about half its weight and the effort force is about half. But both strands must shorten by the lift height, so the effort moves twice as far: less force over more distance.
Lower. Friction in the pulleys (especially spools on pencils) and the weight of the moving pulley itself both add to the effort force.
Work in comes out slightly bigger than work out. The pulleys don't save work; the extra is lost to friction (and lifting the moving pulley).
Change: the type of pulley. Measure: effort force (and cord pulled) for the same lift. Keep the same: the jug and water amount, the number of strands, the lift height, the cord, pulling slowly and straight.
Examples: cranes, flagpoles, sailboat rigging, window blinds, tow trucks, gym weight machines, elevators. Strand counts vary; any reasonable number is fine.