1. Work and Machines
Work: is the transfer of energy that occurs when a force makes an object move
For work to be done, a force must make something move
ex: pushing on something that doesn’t move is not doing work

2. Two conditions have to be met to do work on an object
1. object has to move
2. motion of the object must be in same direction as force applied
When work is done, a transfer of energy always occurs
So: Energy is also the ability to do work (not just the ability to cause change)

3. Work = force X distance Calculating Work OR W = F X d
*Units for work are Joules
(Practice Calculating Work)

4. Using Machines Machines: a device that makes doing work easier
Machines increase the force applied to an
object OR increase the distance over which a force can be applied
Machines can also change the direction of an applied force
Ex: car jacks, ramps, wedges

5. Effort and Resistance Forces
Two forces are involved when a machine is used to do work
Effort force: the force applied to the machine
Resistance force: the force applied by the machine to overcome resistance
Ex: when you pull a nail out w/a hammer, effort force is applied to the handle, resistance force is applied to the nail by the claw

6. Efficiency: a measure of how much of the work put into a machine is changed into useful output work by the machine
High efficiency means less heat produced from friction
Efficiency = W output/W input X 100%
Friction causes output work to always be less than the input work
SO: Efficiency of a real machine is always less than 100%