Movable Pulleys - Simple Machines - What are pulleys? How do pulleys work? answers questions

Movable Pulleys

Bike hoist pulleys
Bike hoist pulleys

A movable pulley is a way to use a pulley to make it easier to move heavy things - to get a mechanical advantage. In the picture, someone is trying to pull their bike up to the ceiling so it will be out of the way. They've used two fixed pulleys, attached to the ceiling, and two movable pulleys, hooked on to their bike.

The fixed pulleys make it easier to pull the bike up, by changing the direction of force so he can pull down instead of having to lift the bike up. But the movable pulleys give him a mechanical advantage too:

Here's a video of someone actually using a bike hoist:

Fixed pulleys
Learn by doing - pulleys

Bibliography and further reading about simple machines:

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Professor Carr

Karen Eva Carr, PhD.
Assoc. Professor Emerita, History
Portland State University

Professor Carr holds a B.A. with high honors from Cornell University in classics and archaeology, and her M.A. and PhD. from the University of Michigan in Classical Art and Archaeology. She has excavated in Scotland, Cyprus, Greece, Israel, and Tunisia, and she has been teaching history to university students for a very long time.

Professor Carr's PSU page

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