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##### Using Machines

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**1. Machines**• A machine is a device that makes doing work easier. • Machines make work easier by • (a) increasing force • (b) increasing distance • ‘(c) changing direction**2. Effort Force**• Effort force is the force applied to the machines • Fe**3. Resistance Force**• Resistance force is the force applied by the machine to overcome resistance • Fr**4. Work Done by a Machine**• Two types of work: the work done by you on the machine and the work done by the machine • Input Work: Win – work done by you on the machines • Output Work: Wout – work done by the machines**5. Conserving Energy**• Recall, energy can not be created or destroyed; it is transferred • So, Wout can NEVER be greater than Win; typically Wout is always less than Win because some of the energy changes to heat due to friction**6. Ideal Machines**• No friction exists and therefore • Work in ==== Work out**7. Mechanical Advantage**• Mechanical Advantage – the number of times a machines multiplies the effort force • Calculated by dividing the Resistance Force by the Effort Force**8. IMA vs MA**• Difference between ideal mechanical advantage and mechanical advantage is friction. • IMA is a calculation assuming no work input is lost to friction and converted to heat. • MA takes friction into account and is a realistic number.**9. Efficiency**• Efficiency is a measure of how much of the work put into a machine is changed into useful output work by the machines (ie not transferred to heat via friction) • Wout/Win * 100%