1. CHAPTER 4

2. Work
-What is Work?
-How to Calculate Work?
-How to Calculate work in a gas?

3. ‘ Work is done when
A forces moves to
In Physics point at which it acts
in the direction of
NO! Work is not going to the office…
the forces. ‘
Work Done = Force X Distance moved by force in the direction of the force
(Joules) (Newton) (Metre)

4. Examples
50 N
30 N
10M
Work done= 50N-20N X 10
20NX10
200 Joules toward the right.
30 degree
10m So
=40xcos30 X 10M
To count the work done in an object,
(Force) (Direction)
the force must be in the same direction in the direction they move.

5. WORK DONE IN AN EXPANDING GAS
Work Done By The Gas = Force X Distance Moved
(Joule) Newton (N) Metre (m)
Work Done On The Gas = Pressure X Change in Volume
(Joule) Pascal (Pa) Metre cube (m^3)
When the “gas expands”,work is done by gas. (Distance is moved)
If the gas “Contracts” ,then work is done on the gas.(Volume increase or decrease)

6. -What is Energy?
-What is Potential Energy?
The ability to do work.
-What is Kinetic Energy?
ENERGY

7. What Is Energy?
-Energy is the ability to do work.
-Energy cannot be destroyed,nor created.
-Energy can only change form.
-Every move that we’re doing are consisted of Energy.
-Energy have the SI of Joule.

8. Potential Energy
3KG
Potential energy is the ability of an object to do work
as a result of its position or shape.
10m
Potential Energy= Mass X Gravity X Height
(Joule) Kilograms (Kg) 9.8 m/s^2 Metre (m)
So:
EP= 3 X 9.8 X 10
EP= 294 Joules

9. Kinetic Energy
Kinetic Energy is the energy due to motion.
30 Kg
Velocity= 10 m/s
Kinetic Energy= ½ X Mass x Velocity^2
Joules Kg (m/s)^2
1/2MV^2
So:
Ek= 1/2Mv^2
½ X 20 X 10^2
1000 Joules

10. Energy Conversion and
Conservation

11. Type Of Energy
Energy cannot be created or destroyed.
It can only be converted from one form to another.
Energy Explanation
Here are a few example of the type of Potential Energy Energy Due to position
energy that they can be converted into:
Kinetic Energy Energy due to motion
Elastic or Strain Energy due to stretching an object
Energy
Electrical Energy Energy associated with moving electric
energy
Sound Energy A mixture of potential and kinetic energy
Wind Energy A particular type of kinetic energy
Light Energy Energy released during chemical reaction
Solar Energy Light energy from the sun

12. Efficiency
What Is Efficiency ?
Efficiency gives a measure of how much
of the total energy may be used and is not lost
Energy Efficiency Formula?
Efficiency = Useful Work Done/Total Energy Input X 100

13. The Deformation Of Solid
-Hooke’s Law
-Strain Energy
-Stress Energy
-Young Modulus

14. Hooke’s Law
What is Hooke’s law?
Hooke’s law states that, provided the elastic limit is not exceeded,
the extension of a body is proportional to the applied load.
Force =K.Extension
(Newton) (Metre)
Where K is constant . It is known as elastic constant
or spring constant.
Force is directly proportional to Extension

15. Strain Energy
Strain Energy is energy stored
in a body due to change of shape.
Formula
Straign Energy W = ½ K.Extension^2
Metre
Joules

16. The Young Modulus
What is The Young Modulus?
It is a constant of a particular material which enable us to find extensions
knowing the constant and the dimension of a specimen.
Stress
Young Modulus = --------------------------------
Strain
Stress = Force/Area Normal to the force
Strain = Extension/Original Length If there is a tie,the area of the circle in the tie is the diameter.
Because it is a normal to the force

17. The behaviour of different material
under tensile stress.
Brittle Material Ductile Material
A brittle material will snap when exceeding A ductile material will expand and fractured
the ultimate tensile stress.EX:GlassFibre. when exceeding
the ultimate tensile stress.EX:Metals

18. The behaviour of different material
under tensile stress.
ENERGY

19. Thermal/Heat Energy

20. Specific Heat Capacity
What is a specific heat capacity?
It is the constant to produce an energy with
a certain mass and changes in Temperature.
Formula
Q = Mass X C X Changes in temperature

21. Thermal (Heat) Capacity
What is a Thermal (heat) capacity?
It is the quantity of the heat energy required to raise the temperature
of the whole body by one degree.
Formula
Q = C X Changes in temperature

22. Specific Latent Heat
What is a specific Latent Heat?
It is the heat energy required to convert unit mass of solid to liquid
without any change in temperature.
Formula
Q = Mass X Latent heat of Fusion/Vaporisation
Latent heat of Fusion (Lf) = when Ice turns into water or water turns into Ice
Latent heat ofVaporisation(Lv) = when water turns into gas or gas turns into
water.

23. POWER

24. What is Power?
Power is the rate of doing work.
Power have the SI of Watt/Second.
Usually Your bills in the mail,consisted of KW/H instead of W/s .
Formula
Power= Work done/Time Taken
Power=Force X Speed

25. Moment Of Force

26. Moment Of Force
What Is Moment Of Force?
Thetha
It is the turning effect of a Force. ------------------------------------------
Moment Of Force = Force x distance
Nm N m

27. Couples
What is a Couple?
A couple consist of two forces , equal in magnitude
F but opposite in direction whose lines of
action do not coincide.
r
r Moment of Force = F x 2r
F

28. The Principle of Moments
It is stated that ,for a body to be in rational equilibrium,
the sum of the clockwise moments about any point must equal
the sum of the anticlockwise moments about the same point.
30 m
10 m 20 m
0.1 N (10 x 0.1)=(20x0.1) + 30f 0.1 N F
Sum of the clockwise moments= (10 x 0.1) 1=2+30f
Sum of the anti clockwise = (20 x 0.1) + 30F Moments= 1-2 // -30 = - 29.

29. Equilibrium:
What the center of Gravity?
The center of gravity of an object is the point at which
the whole weight of the object may be considered to act.
For a body to be equilibrium:
-The sum of the forces in any direction must be zero.
- The sum of the moments of the forces about any point must be zero.

30. Thank You