1. Section 1: Work

2.  Explain the meaning of work.  Describe how work and energy are related.  Calculate work.  Calculate power.

3. Backpacking is a lot of fun, but it also can be a lot of work. Whether hoisting the pack onto your back to start the hike or trudging up a long hill, you’ll need to exert a good deal of effort to get to the next camp. 1.Compare the effort exerted by a backpacker moving over level ground to that exerted by a backpacker moving uphill. 2.How do you think the weight of the backpack affects the amount of force needed to move it?

4.  Work: transfer of energy that occurs when a force makes an object move

5.  For work to occur, two conditions must be met: 1. an object must move 2. the motion of the object must be in the same direction as the applied force on the object.

7.  Work and energy are related.  Energy is always transferred from the object doing the work to the object on which the work is being done.

9.  Work is done on an object only when a force is being applied to the object and the object moves.  If the object does not move, then no work is being done!

10.  Work equals force (in newtons) times distance  W = Fd  W  work, measured in joules (J)  F  force, measured in newtons (N)  d  distance, measured in meters (m)

11.  You push a refrigerator with a force of 100 N. If you move the refrigerator a distance of 5 m while you are pushing, how much work are you doing?

12.  F = W/d  d = W/f

13.  A lawn mower is pushed with a force of 80 N. If 12,000 J of work are done in mowing a lawn, what is the total distance the lawn mower was pushed?

14.  The brakes on a car do 240,000 J of work in stopping the car. If the car travels a distance of 50 m while the brakes are being applied, what is the force the brakes exert on the car?

15.  Power: amount of work done in a certain amount of time  rate at which work is done

16.  Power equals work divided by time.  P = W/t  P  power, measured in watts (W)  W  work, measured in joules (J)  t  time, measured in seconds (s)

17.  You do 900 J of work in pushing a sofa. If it took 5 s to move the sofa, how much power did you use?

18.  W = Pt  t = PW

19.  If a runner’s power is 130 W as she runs, how much work is done by the runner in 10 minutes?

20.  The power produced by an electric motor is 500 W. How long will it take the motor to do 10,000 J of work?