WORK,ENERGY AND POWER
WORK AND ENERGY
If the force is constant
Unit of work is the Joule ( J ), where 1 J = (1 N ) ( 1 m ) = 1 Nm
If the force is not constant
Work done by Expanding or Compressing a gas
POTENTIAL ENERGY AND KINETIC ENERGY
LEARNING OUTCOMES
1. Derive and use the formula: Potential Energy ( U ) = mgh, near the surface of the Earth.
2. Derive the formula: Kinetic Energy = ½ mv 2 .
3. State and use the Work-energy theorem.
4. Apply the Principle of conservation of energy in situations involving kinetic and potential energy.
Change K.E = Work done
Gravitational Potential Energy
Elastic Potential Energy
2
0 2
1
,
keUdekeU
e
UkekeF
e
UF
UKeFW
e
Elastic Potential Energy
From the principle of t conservation of energy
This value is known as the elastic potential energy, i.e energy stored in thespring.
Since, F = ke, then
W= ½ ke2.
Elastic Potential Energy
Conservation of Energy
MECHANICAL ENERGY
CONSERVATION OF ENERGY
DERIVATION THE FORMULA
mghmv 22
1
Work-energy Theorem
The work done by the net force of an
object is equal to the change in the
Kinetic Energy.
CONSERVATION OF ENERGY
PRINCIPLE OF CONSERVATION OF ENERGY
Principle of conservation of energy –
States that the energy cannot be created or destroyed but can be converted from
one form to another form of energy.
The total energy which is equal to the sum of gravitational potential energy and kinetic energy is constant.
KUKU
KUE
KUE
0
This equation shows that the gain in gravitational potential energy is equal to theLoss in kinetic energy.
UK
CONSERVATION OF ENERGY
CONSERVATION OF ENERGY
CONSERVATION OF ENERGY
CONSERVATION OF ENERGY
PROBLEMS ABOUT WORK AND ENERGY
PROBLEMS ABOUT CONSERVATION OF
ENERGY
Power and Mechanical Efficiency
LEARNING OUTCOMES
1. Derive and use the formula; P = Fv2. Use the concept of Efficiency to solve problems
Power and Mechanical Efficiency
Power and Mechanical Efficiency
Power and Mechanical Efficiency
Power and Mechanical Efficiency
Power and Mechanical Efficiency
Power and Mechanical Efficiency
Power and Mechanical Efficiency
Power and Mechanical Efficiency
J
J
Example:
THE END