Prepared By: Shakil Raiman
The amount of work done by a constant force is defined as the
product of the force and the distance moved in the direction of
force.
 Work Done = Force × Distance Moved
 W=Fs
 Unit : J (joule)
 1J=1N×1m
 It is a scalar quantity.
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Work is done only when there is distance moved.
Case – 1: A book is on a table. In this case the book giving force on the
table or the table is giving force on the book. But there is no distance
moved. So no work is done.
That is, work done = 0 J
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Work is done only when there is distance moved.
Case – 2: Suppose, someone is lifting a book from the ground and
putting it on the table. As there is distance moved, work is done.
If the book has weight 5 N and the table is 1 m high,
Work done = 5 N × 1 m = 5 J
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Case – 3 : One person is pushing a wall. As the wall does not
move, there is no work done by the force.
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Case – 4 : One person is pushing a chair. As the chair moves,
there is work done by the force.
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Energy is defined as the ability to do work.
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It is a scalar quantity.
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Unit: J (joule)
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In O’Level we will study only two types of mechanical energy
(GPE and KE) and Electrical energy. (also Heat energy for CIE
syllabus)
Sl No. Forms of Energy
Examples
01
Chemical Energy
Fuels (oil, coal, petrol, gas), electric cell, food, explosives
02
Electrical Energy
The energy associated with the current in electrical
appliances as motor, heater
03
Nuclear Energy
The energy released from nuclear reactions
04
Kinetic Energy
A moving car, a flying aeroplane
05
Gravitational Potential
Energy
a waterfall, raised object
06
Thermal Energy
Given by hot object
07
Elastic Potential Energy
compressed or stretched spring or rubber band
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Energy possessed by an object due to its motion is called
kinetic energy.

Kinetic Energy = ½ mv2
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Any free falling object or pendulum has maximum kinetic
energy when it is close to the ground or when it is it’s minimum
position.
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Unit: J
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Energy possessed by an object due to its motion is called
kinetic energy.

Kinetic Energy = ½ mv2
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Any free falling object or pendulum has maximum kinetic
energy when it is close to the ground or when it is it’s minimum
position.
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Unit: J
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Energy possessed by an object due to its position is called
gravitational potential energy.

Gravitational Potential Energy = mgh

Any free falling object or pendulum has maximum gravitational
potential energy when it is at its maximum height from the
ground.
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Unit: J
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Energy can neither be created nor destroyed. Energy can be
changed from one form to another or can be transferred from
one object to another.
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Power is the rate of doing work or rate of converting energy.
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Power = Work done / Time taken
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or Power = Energy converted / Time taken
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It is a scalar quantity.
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Unit: W (Watt)
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Power is the rate of doing work or rate of converting energy.
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Power = Work done / Time taken
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or Power = Energy converted / Time taken
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It is a scalar quantity.
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Unit: W (Watt)
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Renewable Energy Source: Energy source which will not finish
after used or takes short time to reproduce.
Example: Sunlight, Wind Energy, Tidal Energy, Geothermal
Energy.
Non-Renewable Energy Sources: Energy source which will
finish after used once or takes millions of years to form.
Fossil Fuels (Oil, Gas, Coal)
Transducer or Alternators converts energy from one form to
other.
 Examples:
 Bulb: Electrical to Heat and Light
 Speaker: Electrical to Sound
 Generator : Kinetic to Electrical
 Motor : Electrical to Kinetic
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We use different ways to show how energy is transferred
and converted.
Most of the time block diagram is used.
Check on board.
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Sankey Diagrams: Sankey diagrams are a simpler and
clearer way of showing what becomes of an energy input to
a system. The energy flow is shown by arrows whose width
is proportional to the amount of energy involved. Broad
arrows show large energy flows and narrow arrow show
small energy flows.
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Wish you all very good luck and excellent
result.