Igcse Physics Revision NotesO Level Physics Revision Notes

Work Energy And Power


Work done by a constant force is given by the product of the force and the distance moved in the direction of the force.

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Work = Force (N) Γ— Distance (m)

The SI unit for work is Joule (J).


Work is not done when

  • The direction of the applied force and the direction in which the object moves are perpendicular to one another.
  • The force is applied on the object (such as the wall) but the object doesn’t move.



Energy can be defined as the ability to do work.

SI unit: Joule (J)

Types Of Energy:

Types Of Energy - Work Energy And Power

Kinetic Energy:

It is the energy possessed by a body by virtue of its motion .In simpler words ,any moving object has kinetic energy.

Kinetic Energy

SI unit: Joules (J)


Gravitational Potential Energy:

Gravitational potential energy = Mass Γ— Gravity Γ—Height

GPE =mgh

Kinetic And Potential Energy In Simple Pendulum:

Potential and Kinetic Energy in Pendulum

Conversion And Conservation Of Energy:

Energy can neither be created nor destroyed in any process. It can be converted from one form to another or transferred from one body to another, but the total amount remains constant.



Power is defined as the rate of work done or energy converted.

Formula of Power

SI unit for power is Watts (w)

Therefore work =power Γ— time

Energy =power Γ— time

Efficiency Of A Machine:

Efficiency of a machine is a ratio of output work to input work.

It shows the percentage of output work from the input work.

Formula Of Efficiency


No machine is hundred percent efficient because there is always energy in the form ofΒ  heat and sound.

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