Using Machines

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%