FORCE

FORCE : You are doing work when you use a force to cause motion. Machines make work easier, but they need energy to do work. A person is usually the source of energy for a simple machine. A person uses a force to operate a simple machine. A force is a push or pull. The force applied to to the machine is called work input or effort force.

Machines do work too. The machine exerts force over a distance. This is called output force. The work the machine does is called the work output. The work output is used to move the "force" you and the machine are trying to move or overcome. This "force" is called the resistance or load.
Machines do not increase the amount of force or effort put into the machine. The amount of work that comes out of a machine will never be more than the work that is put into the machine. A machine makes work easier. Machines make work easier by multiplying either the force or the distance. Study the chart below.

work Input -> MACHINE -> work Output

effort force/distance -> multiplies effort -> exerted over shorter distance
effort force/distance -> multiplies distance -> output force less

The number of times the machine multiplies the effort force is called the Mechanical Advantage. (This is a link to "mechanical advantage")The mechanical advantage can be found by dividing the force of the machine by the force you used on the machine.

Mechanical Advantage=resistance (load)
effort force (force into machine)

ACTIVITY: How does mechanical advantage change?

MATERIALS:

lever
variety of weights
1 wooden block
1 weigh block (record)

1. Place block on top of ruler.
2. Place fulcrum under ruler.
3. Place weights on ruler end, opposite of the block.
4. Add weights (effort force) until block moves.
5. Calculate total weight of effort force.
6. Use ratio to calculate mechanical advantage
7. Does the mechanical advantage change if you move the fulcrum?

Formula for finding the mechancial advantage of an inclined plane:


MA = Inclined plane length
Inclined plane height

Formula for finding the mechanical advantage of a pulley:

MA = the # of supporting straps

Formula for finding the mechanical advantage of a lever:

MA = the distance from the fulcrum on the larger side
the distance from the fulcrum on the shorter side

To WORK IS SIMPLE WITH SIMPLE MACHINES