 # Simple Machines Machines Lever Inclined plane Pulley Screw Wedge Wheel & axle.

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Simple Machines

Machines Lever Inclined plane Pulley Screw Wedge Wheel & axle

Machines Device to multiply force or change its direction Can’t increase work done Work put into machine must be at least as great as the work output of machine

Machines Since work is force times distance, input force can be decreased by increasing input distance: force is “multiplied” Work is made easier because less force is needed Sometimes output distance is increased by increasing input force: distance is multiplied

Efficiency Work output divided by work input (x 100 for %) A measure of losses due to friction Efficiency is always less then 100%

Mechanical Advantage A measure of how much the effect of the force is increased Actual M.A. is ratio of output force to input force Theoretical M.A. can be found from the design of the machine

Mechanical Advantage For lever, theoretical MA is input distance / output distance For inclined plane it is plane length / height For pulley system it equals the number of cords supporting the weight being lifted

Summary Machines help us do work by using less force over greater distance Mechanical Advantage = output force / input force Efficiency = work out / work in

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