Look at this heavy bag of books. Hands up: would you rather lift it straight up with your hands, or pull a rope that goes over a wheel above it? What might change about how you pull?
Today we find out how pulleys and gears change the way a force works.
Remember the bag of books. That bag is the load. The pull of your hand is the effort. The wheel a rope runs over to help you lift is a pulley.
How might a single pulley change the direction of your pull?
Builders and bike makers use these same ideas so heavy things and spinning wheels can do useful jobs. We will meet gears after the pulley work.
Today you build a real pulley from things in the classroom. A metre stick holds it up, a roll of tape is the wheel, and a string carries your pull to a bag of books.
We will build one at the front first, so watch how it comes together. Then follow the six moves on the card below, one at a time. Look at the picture for each move before you start it, and do not go on until the check under the move is true.
Two of you set up the desks and the stick. One ties the bag. One runs the string over the roll. When it works, swap jobs so that everyone gets to pull.
Same bag both times: only the way you lift changes. Keep the load the same so the comparison is fair.
First, lift the load straight up with your hands (careful and slow). Then lift the same load using your pulley.
In your group, choose how you will judge which felt easier to control (for example: steadier lift, less wobble, or easier to stop halfway). Talk about what changed about the direction of your pull, and agree one clear sentence your group will stand by.
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