Grandpa Fenn's Workshop
The Pulley Lab
Grandpa hoists a heavy crate up to the loft with one finger. He says the rope does the work. Here is how.
Grandpa Fenn's Workshop
Grandpa hoists a heavy crate up to the loft with one finger. He says the rope does the work. Here is how.
The crate weighs 80. Pick a way to lift it. Then pull the rope with the slider and watch the numbers.
Start with the plain lift. Then try the others.
Grandpa grins. Four strands of rope and one finger. That is the trick.
A pulley is a wheel with a rope over it. A fixed pulley does not make the pull smaller. It just lets you pull down instead of up.
A moving pulley hangs on the crate. Now two strands of rope share the weight. Each strand carries half.
Add more strands and each one carries less. With four strands you pull with a quarter of the weight.
But look at the rope. For every bit the crate goes up, you pull four times as much rope.
Poppy counts the strandsCount the strands that hold up the crate. Each one carries a share.
More strands means a lighter pull.
More strands also means more rope to pull. The trade is always fair.
Big word for the day. Pulley. A wheel with a rope that helps you lift.