Science

2. Objectives:
1. Find out the importance of work and
energy and its relationship to power.
2. Identify the situations in which work is
done or not.
3. Differentiate potential energy and kinetic
energy.

3. WORK ENERGY POWER
Definition Work is said to be
done when a force
applied to an object
moves that object.
In physics, we can
define energy as the
capacity to do work
and to cause change.
Power can be
defined as the rate
at which work is
done i.e. energy
converted
Formula W = F × d P.E. = mgh P = W/t
Unit The SI unit of work
is the
joule (J)
N/m (Newton-
meter)
1 J = 1 N/m
The SI unit of energy
is named in honour
of James Prescott
Joule
joules(J)
The SI unit of
power is
watt (W)

4. Which work has been done?

6. Work
Work is said to be done when a body or object
moves with the application of external force in the
direction of the force applied.
The object must move.
1 J = 1 N/m W = F × d

7. A push of 10 N, moves an object 3 meters,
does 30 J of work.
Formula: W = F x d
Solution: W = 10N x 3m
Answer: W = 30 J or 30 N/m
(A Newton-meter is the same thing as a joule)

8. Example
An object is horizontally
dragged across the
surface by a 100 N
acting parallel to the
surface. Find out the
amount of work done by
the force in moving the
object through a distance
of 8 m
W = F × d
W = ?
F = 100 N
D = 8 m
W = 100 N x 8 m
= 800J

9. What is Power?
Power is a physical concept that has several different
meanings, depending on the context and the
information that is available. We can define power is
the rate of doing work. It is the amount of energy
consumed per unit time. Time used is seconds.
P = W/t

10. Frank does 2400J of work in climbing a
set of stairs. If he does the work in 6
seconds, what is his power of output?
Formula: P = W/t
Solution: P = 2400J / 6 secs
Answer: 400W

11. ENERGY
❖ In physics, we define energy as the
capacity to do work and to cause change.
❖ The SI unit of energy is named in honour of
James Prescott Joule joules (J)
❖ Everything that happens in the world uses
energy! Most of the time we can’t see
energy, but it is everywhere around us!

12. Law of Conservation of Energy
Energy can neither be created nor destroyed.
It can only be transformed from one kind to another.
The total amount of energy remains constant.

13. Forms of Energy
● Wind energy
● Hydro energy
● Mechanical energy
● Electromagnetic energy
● Chemical energy
● Electric energy
● Nuclear energy
● Elastic energy
● Gravitational energy
● Thermal energy
● Heat Energy
● Light Energy

14. Example of transformation of one energy to
another form of energy

15. All forms of
energy are
either Kinetic
Energy or
Potential
Energy
Kinds of Energy

17. • The energy stored in an object.
• "Potential" simply means the energy has the
ability to do something useful later on.
● The higher an object and the more mass an
object has, the more potential energy it
has.
Potential Energy

18. Examples of Potential Energy
A stretched
rubber band
Water at the top
of a waterfall
Yo–Yo held in your
hand

19. Which object has
more potential
energy?
A.
B

20. Changing an object's’ height can change its
potential energy.

21. Potential Energy Converted
to Kinetic Energy

22. Kinetic Energy
•The energy of a moving object.
•"Kinetic" means movement!
•When stored energy is being used up, it is making things
move or happen.
•The faster the object moves, the more kinetic energy is
produced.
•The greater the mass and speed of an object, the more
kinetic energy there will be.

23. Examples of Kinetic Energy

24. When these objects move at
the same speed, which will
have more kinetic energy?

25. The semi- truck has more
mass; therefore, more kinetic
energy

26. •An object has the MOST kinetic
energy when it’s movement is the
GREATEST.
•When an object has the LEAST
potential energy, it has the MOST
kinetic energy.

27. Can you identify where is the kinetic energy and
the potential energy in this example?