Work & Power

Embed

Social
Select the file type you wish to download
Slide Content

Slide 1  Work & Power

Slide 2  Work
 When you apply a force to an object and the object moves in the same direction as that force, you are doing work.
 Examples.
 When you push a box across a floor, that’s work.
 When you push on a wall, but it doesn’t budge. That is not work.

Slide 3  Calculating Work
 Work = force x distance
 Example:
 You apply a force of 12 N to a box and move it 8 m across the floor. How much work was done?
 The units of work are the “Newtonmeter” (N·m), which is also called a Joule (J).

Slide 4  Power
 Power is the rate at which work is done.
 If an object has more power than another it either:
 Gets more work done in the same amount of time
 Gets the same work done in a shorter amount of time
 Example: you and a friend are hiking up a hill carrying backpacks that make your mass identical. If you reach the top before your friend, you hiked with more power.

Slide 5  Calculating Power
 You do 10 J of work in 2 seconds:
 The units of power are watts (W).

Slide 7  Machines
 Machines are devices that makes work easier in at least one of these three ways:
 1. Change the amount of force you exert
 2. Change the distance over which the force is exerted
 3. Change the direction in which you exert the force

Slide 8  Machine Example

Slide 10  Input & Output Force
 The force you exert on machine is called the input force.
 The force the machine exerts is called the output force.
 Since machines make work easier, the output force can never be less than your input force unless you change the distance or direction.

Slide 11  Mechanical Advantage
 The ratio of the output force to the input force is called the mechanical advantage.
 Mechanical advantage is a ratio so it does not have units.

Slide 12  Mechanical Advantage Example
 A pulley system allows you to apply 10N of force and lift a box with a force of 15N. What is the mechanical advantage of the pulley system?