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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%