Machines, Mechanical Advantage and Efficiency

What is a Machine?  A machine makes work easier and more effective.  A machine never changes the amount of work needed to do a job.  HOW IS THAT?

Input Work = Output Work W= 1N x 4mW= 4N x 1m 4 J

Multiply Distance Input Work = Output Work W= 4N x 1mW= 1N x 4m 4 J

Change Direction Input Work = Output Work W= 2N x 2m 4 J

A machine makes work easier by CChanging the amount of force you exert

 Changing the distance over which you exert your force

A machine makes work easier by CChanging the direction in which you exert your force.

A machine can make work easier by 1. Multiplying force 2. Multiplying distance 3. Changing Direction

Input Force “Effort Force” TThe force you exert on the machine

Output Force “Resistance Force”  The force exerted by the machine

Mechanical Advantage  The number of times a force exerted on a machine is multiplied by the machine.

Mechanical Advantage IIf a machine has a mechanical advantage of 5, that means it multiplies the force by 5 times ((5 times easier)

Mechanical Advantage Actual Mechanical Advantage= Output force Input force

Mechanical Advantage of Multiplying Force  The mechanical Advantage is greater than 1  The machine multiplies your force  The output force is greater than the input force.

Efficiency of Machines  The efficiency of a machine compares the output work to the input work.  Part of the work done by a machine is wasted on friction

Calculating Efficiency Efficiency = Output Work Input Work X 100%

Actual Mechanical Advantage  The mechanical advantage that a machine provides in a real situation.  Depends on the efficiency of the machine

Ideal Mechanical Advantage  The mechanical advantage of a machine without friction.  The more efficient a machine is, the closer the actual mechanical advantage is to the ideal mechanical advantage.

Machine’s Efficiency  Machine (a) 95 % efficient (AMA)  5 % lost due to friction  Machine (b) 75 % efficient (AMA)  25 % lost due to friction  Machine (c) 100 % efficient (IMA)  perfect machine no friction  Machine (d) 25 % efficient (AMA)  75 % lost due to friction  What machine will run the hottest?  How can you increase the machine’s efficiency