grade 8 science lesson about what is WORK

1. Our Father
Who art in heaven,
Hollowed be Thy name,
Thy kingdom come,
Thy will be done
On earth as it is in heaven.
Give us this day our daily bread
and forgive us our trespasses
as we forgive those who
trespass against us,
and lead us not into temptation
but deliver us from evil.
Amen
Opening Prayer

3. RECALL

4. QUARTER 1 -
MODULE 3: WORK

5. MOST ESSENTIAL LEARNING
COMPETENCY
•Identify and explain the factors that
affect potential and kinetic energy.
•(S8FE-Ic-20)

6. Objectives:
•1.Define work scientifically
•2.Identify situations in which work
is done and in which no work is
done.

7. What is
WORK?

8. Work
- A force acting upon an object to cause a
displacement.
Displacement
- Distance moved by an object as a result of the
forces action

9. Work
- being done when all the following conditions
are satisfied
a. A force is exerted on the object
b. The object moves
c. The motion is in the direction of the force.

10. Work is done.. If the object you push
moves a distance in the direction towards
which you are pushing it.

11. No work is done.. If the force you exert
does not make the object move

12. No work is done.. If the force you exert
does not make the object move in the same
direction as the force you exerted.

13. Example:
Work done
A horse pulling a plow through the fields.

14. Example:
Work done
A father pushing a grocery cart down the aisle
of a grocery store.

15. Example:
Work done
A weightlifter lifting a barbell above her head.

17. Work done or No work done?

18. CALCULATING
WORK

19. • Force is measured in
- Newtons (N)
• Distance/displacement measured in
- meters (m)
• Newton (N) times meter (m) = JOULE
• Work like energy is measured in
- Joules (J)

20. * The symbol for Work is capital W.
The work done by a force can be calculated as W=Fd
Unit
W = Work N.m or Joule(J)
F = Force N
d = displacement m

21. • The unit of Joule
- Named after the English
physicists James Prescott
Joule
- also a unit of energy.

22. Example:
1. A book weighing 1.0 N is lifted 2m. How much work was done?
Given:
F = 1.0 N
d = 2 m
W= ?
Formula:
W = Fd
Solution:
W = Fd
W = (1.0 N) (2m)
W = 2 N.m or 2 Joule

23. Example:
2. It took 50 J to push a chair 5m across the floor. With
what force was the chair pushed?
Given:
W = 50 J or 50 N.m
d = 5 m
F= ?
Formula:
F = W/d
Solution:
F = W/d
F = 50 N.m / 5 m
F = 10 N

24. Example:
3. It took a mass of 200 kg accelerating at 4 m/s2
of force to push
a car 4 m. How much work is done?
To get the force: F=ma
Given:
m = 200 kg
a = 4 m/s2
d = 4 m
W = ?
Solution:
F =ma
F = (200 kg) (4 m/s2
)
F = 800 N
W = Fd
W = (800 N) (4m)
W = 3200 N.m or 3200 J

26. Let us check
your
understanding!

27. Seatwork:
Work or no work?
A = Work B = No work
1. A teacher applies a force to a wall and
becomes exhausted.
2. A man pushing a stalled car, but the car
doesn’t move.
3. A book falls off a table and free falls to the
ground.

28. Seatwork:
Work or no work?
A = Work B = No work
4. A waiter carries a tray full of meals above
his head by one arm across the room.
5. A rocket accelerates through space.

29. Seatwork:
Work or no work?
A = Work B = No work
1. A teacher applies a force to a wall and
becomes exhausted.
2. A man pushing a stalled car, but the car
doesn’t move.
3. A book falls off a table and free falls to
the ground.
B
B
A

30. Seatwork:
Work or no work?
A = Work B = No work
4. A waiter carries a tray full of meals
above his head by one arm across the
room.
5. A rocket accelerates through space.
B
A