This document discusses the concept of work in physics. It defines work as the product of the force applied and the distance an object is displaced in the direction of the force. It provides examples of situations that do and do not represent work being done. It also discusses power, defining it as the rate of doing work, or work divided by time. Several example problems are provided to demonstrate calculating work and power in different scenarios.

1. Work
Grade8- Science
Power

4. 8 Letters

5. 4 Letters

6. 6 Letters

7. People Power
Strength
Knowledge
Work
Power
Energy
Study
Work Smart
Work Hard Labor
I’ve Got The
Power
Joules
Watts

8. Word Bank

9. What is
WORK?

10. Which has done WORK?
Figure A Figure B
FApp FApp
d

11. Which has done WORK?

12. What is
WORK?

13. ForceDisplacement
Object
Same
Direction

14. WORK
orce Displacement
=

15. Read the following statements
and determine whether or not
they represent examples of work.
Application

16. A teacher applies a force to a wall and
becomes exhausted.

17. A book falls off a table and free falls to
the ground.

18. A rocket accelerates through space.

19. With your seatmate, answer and discuss the
following. Write your answer in your notebook.
1.A boy running across a playground.
2. A mother dancing with her baby in her arms.
3. A basket being lifted.
4. A person in an ascending elevator.
5. A stone whirled around a horizontal circle.
6. A big box dragged across the floor.
7. A man climbing up a tree.
8. A girl walking up the stairs.

20. Example Problem 1
•An 80 N force has been applied
to a block and move it 20 m
along the direction of the force.
How much work has been done
to the block?

21. Example Problem 2
•Calculate the work done when
a 20-N force pushes a cart 3.5
m?

22. Example Problem 3
•It will take 3000 Joules of energy to
push a large moving box up a ramp
and into the back of a truck. If the
length of the ramp is 15 meters, how
much force will be required to
accomplish this task?

23. Example Problem 4
•If 68 Joules of work were necessary to
move a 4 Newton crate, how far was
the crate moved?

24. On your own
1. Tommy does 15 Joules of work to push the pencil over 1 meter. How much force
did he use?
2. Angela uses a force of 25 Newtons to lift her grocery bag while doing 50 Joules of
work. How far did she lift the grocery bags?
3. The baseball player does 1234 Joules of work when hitting a baseball into left
field. Assuming the baseball landed 100 meters away from home plate, how
much force did the player use to hit the ball?
4. How much work is required to lift a 360 kilogram piano to a window whose height
is 10 meters from the ground?

25. ABCD
work

27. more work?
greater power?
more tired?

28. =Work/time

29. Example Problems
1. A student who weighs 500 Newtons climbed the stairs from the
first floor to the third floor, 15 meters above, in 20 seconds.
How much work did she do? What was her power?
2. A box is pushed across the floor for a distance of 5 meters with
a force of 50 Newtons in 5 seconds. How much work was
done? What is the power?
3. If it takes 50 seconds to lift 10 Newtons of books to a height of
7 meters, calculate the power required.
4. The power rating of an electric lawn mower is 2000 watts. If
the lawn mower is used for 120 seconds, how many joules of
work can it do?
5. A 750 watt hairdryer is used for 60 seconds. How many joules
of energy are used?

30. 3-2-1
Let’s sum up!

31. “Knowledge is Power”
Why is
knowledge
power?