1. Work

2. Work …is a force acting through a distance. In other words...
Work is only done, when a force moves an object
And the object must be moved in the direction of the force
In other words...
Work = Force x distance
(W = Fd) d

3. Work cont. Is work done in the following examples...
1.You push as hard as you can against a door, but it does not move.
No: there is no movement
2.You lift a basketball off the floor.
Yes: there is force and distance
3.Superman stops a speeding jet.
No: there is not movement in the direction of the force
4.You put your backpack on and carry it to the door.
No: the movement is not in the direction of the force
5.You hold your backpack for five minutes.
No: there is no time involved in work

4. Work cont. Work is measured in newton-meters (Nm) 1 Nm = 1 Joule (J)
-the newton is from force
-the meter is from distance
1 Nm = 1 Joule (J)

5. Power Horsepower (hp) …is the rate at which work is done.
Power = Work
Time
The unit of power is the watt (W)
1 Watt = 1 joule per second (J/s)
Electricity is measured in kilowatts (kW)
Horsepower (hp)
One hp equals 750 watts

6. Practice Problems
for
Work & Power

7. A car runs out of gas. Fortunately, there is a gas station
nearby. You must exert force of 715 N on the car in order to
move it. By the time you reach the station, you have done
2.72 x 104 J of work. How far have you pushed the car? W= F= d=
What Formula do you need to use? _____________________
Solve the Problem:

8. The world’s most powerful tugboats, which are built in
Finland, are capable of providing 8.17 x 106 W of power.
How much work does one of these tugboats do in 12.0 s? W= P= d=
What Formula do you need to use? _____________________
Solve the Problem: