ENERGY & POWER
CHAPTER 7
WORK, ENERGY & POWER
Work, W is defined as the product of force,
F and displacement, s in the direction of the
force that is
W=Fs
The S.I unit for work is Joule
SEVERAL ACTIVITIES IN THE DAILY LIFE
CALCULATING WORK DONE
ENERGY & POWER
Energy is defined as the ability to do
work.
The S.I unit for energy is Joule
When a force of 1N is used to move
an object over a distance of 1m in the
direction of force, 1J of energy is used
Power, P is defined as the rate of doing work,
W
The S.I unit for power is watt, W
When 1 Joule of work is done in 1
second(s), power of 1 watt(W) is used that
is 1W= 1 Js-1
EXAMPLE OF CALCULATION OF POWER
IN DAILY LIFE
EXERCISE
POTENTIAL ENERGY & KINETIC ENERGY
GRAVITATIONAL POTENTIAL ENERGY
Gravitational potential energy is the work done
to lift an object to a height, h from the earth’s
surface
RELATIONSHIP BETWEEN WORK AND
GRAVITATIONAL POTENTIAL ENERGY
ELASTIC POTENTIAL ENERGY
Elastic potential energy is the work done to
compress or stretch an elastic material over a
displacement of x from the position of
equilibrium
RELATIONSHIP BETWEEN WORK AND
ELASTIC POTENTIAL ENERGY
A spring is stretched x m with a force of F N, so the
value of force acting of the spring changes from 0 to F
N
KINETIC ENERGY
Kinetic Energy is the energy possessed by
a moving object
PRINCIPLE OF CONSERVATION OF
ENERGY
The Principle of Conservation of Energy
state that energy cannot be created or
destroyed but only be converted form one
form to another form
OSCILLATING SYSTEM OBEY THE PRINCIPLE OF
CONSERVATION OF ENERGY
TRANSFORMATION OF KINETIC ENERGY
& POTENTIAL ENERGY IN A CLOSED
SYSTEM
In a closed system, the Transformation of kinetic Energy
& Potential Energy obey the Principle of Conservation
Energy
Total potential energy & kinetic energy is constant
EXERCISE