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# Pulley Presentation

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## amanda simpson

on 12 December 2012

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#### Transcript of Pulley Presentation

- a simple machine used to change the direction or size of a force using a rope and a grooved wheel Pulleys History of Pulleys - Exact origin is unknown
- Early uses were ropes over branches, but those models had too much friction to work efficiently enough.
- Used in Mesopotamia around 1500 B.C.E.
- First documented use was by Archimedes, a Greek astronomer. Real Life Uses of Pulleys - elevators - flag poles
- cranes - wells How a Fixed Pulley Works You pull on one end of a rope slung over a wheel with a rod going through it, and the wheel turns to change sliding friction to rolling friction, making it easier to lift the object attached to the other end of the rope. Input and Output Force - Input and output forces are always the same
- This pulley reduces work by changing direction of movement
- IMA equals the number of rope sections supporting the object How a Movable Pulley Works A rope is pulled upwards, also changing sliding friction to rolling friction and moving the axle that the rope was riding through. Input and Output Force - Output force is greater than input force
- Direction is not changed
- Each section of the rope pulls up with a force equal to the input force, for a total of double the input force How a Pulley System Works Uses both fixed and movable pulleys Input and Output Force -By using multiple pulleys to reduce force, a pulley system changes the direction and size of the force multiple times
- In a pulley system the output force can be many times stronger than the input force because it uses multiple pulleys Different Kinds of Pulleys - Fixed pulleys
- Movable pulleys
- Pulley systems Mechanical Advantage of the Pulley Pulleys change sliding friction to rolling friction, reducing resistance. Thank you! - Zoe, Amanda, Robert, Liza, and Leo
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