What is the definition fo Work, Energy and Power?
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Work, Energy and Power
Work : If a body gets displaced when
said to be done. work is measure:
d displacement of the along the direction of
force.
If body gets displaced by S when a Force F acts on it
then the work W= F S cos
where 9 — angle between force and displacement
If both force and displacement are in the
w=FS
If force and displacernent are perpendicul& to each
For example, in case of uniform circular mot:icn work
by the force is zero.
Work iS a scalar quantity and its SI unit is joule.
Energy : Capacity Of doing work by a ix»dy is called its
aegy.
Energy isa scalar quantity and its Sl joule.
Energy in a body due to work done on itis
called mechanical energy.
Mechanical energy is of two : 1. Potential Energy
2 Kinetic Energy
Potential Energy : The capacityofdoingwork develcpd
a body due to its position or configuration is called its
energy.
E.uample I. energy of stretched or compressed spring
2, dErgy of water collected at a height 3. energy of spring
watch stretched bow
PE of a bcxiy in the gravitational field of earth is mg”.
where m = mas, g acceleration due to gravity h
of the body from surface of the earth.
Kinetic Energv : Energy possessed by a due to its
is called Kinetic Energy of the body.
If a E»dy of mass m is moving v, thenkinetic
mergy of the bcxiy is mv2
A flying aeroplane has EX’th well as kinetic
Iftwobodieshave same kineticenergy, then thebody
With smaller mass will have higher momentum,
Principle of Conservation of Energy
Energy can neither be created nor can be destroyed.
energy can be from one form to another
Wheneverenergy is utilized in amount
energy is in other form. Hene total energy of
called the
universe always remains the same. This is
ple of conservation of energy.
When a ball is thrown vertically upward i ts potential
energy Increanes. kinetic decreases but the total
energy remains constant.
Some Equipments used to Transform Energy
1. Dynamo
2. Candle
3.Microphone
4. Loud Speaker
5.Solar Cell
6. Tube light
7. Electric Bulb
8. Battery
9 Electric motor
10 Sitar
11 photo cell
Relation between Momentum and Kinetic Energy
KAE where p = momentum mv
Clearly when momentum is doubled. kinetic energy
four times.
Power Rate of doing work is called TXjwer.
If an agent W work in tirne t, ti-æn power of agent
w
Sl unit of is watt named as a to the
scientist James Watt-
watt — joule/ sec.
1 kW-1cPwatt, 1 MW-1Cfwatt
Horse power is a unit Of pwer
I H.P. 746 watt.
1 watt *cond 1 watt 1 second 1 jmvle.
1 watt hour 30) joule
1 kilowatt hour (kWh) — 3S joule
W, kW MW & H.E are units Of pwer-
Ws, Wh. kWh are units of work and energy.