1. Work

2. Work has a specific physics meaning

3. Work W=Fd Energy transferred to an object over a distance
WORK IS ENERGY GAINED OR LOST
W=Fd
Where:
W – Work (J)
F – Magnitude of Force (N)
d – distance (m)

4. Work is scalar (so no direction needed)
BUT Force and distance need to be in the same direction

5. Work Against Gravity
To lift an object (at a constant speed), the force applied is equal to the force of gravity
If you are lifting up, positive work
If you are lowering down, negative work

6. Example 1
Jacob pushes a shopping cart with a force of 500N through 2.0 m. What is the work done?

7. Example 1b
If the shopping cart has a mass of 40kg and all energy is transferred to kinetic energy, how fast will it be moving after the push?

8. Example 2
Krinal lifts an object with a mass of 10kg. The object gains 1000J of gravitational potential energy. How high does she lift it? How high could you lift a 10kg mass using all the energy in a piece of gum?

9. Negative Work Occurs if the force opposes motion
In most cases negative work is done by friction – the energy is taken away and turned into thermal energy
W=-Fd
Where:
W – Work (J)
F – Magnitude of Force opposing motion (N)
d – distance (m)

10. Example 3
Two students are pushing on a car as shown below. The car moves 10m to the right.
How much work does person 1 do?
How much work does person 2 do?
How much energy is gained by the car?

11. Work
Pg 135 # 1,3,4
Pg 136 # 8-10