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Learn about simple machines like levers, inclined planes, pulleys, screws, wedges, and wheel & axle. Discover how machines can multiply force or change its direction, and how to calculate mechanical advantage and efficiency. Explore the concepts of work input and output and understand how machines make work easier.
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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