Work and Power

IGCSE Work and Power Revision

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  • Created by: bethedoc
  • Created on: 03-04-12 16:01

Energy and Work

Work, W = Force, F x Distance, d

This is how you calculate work done, W, in joules when a force, F, in newtons is applied through a distance,d, measured in metre in the direction of the force


  • Doing work involves transferring energy
  • Energy and work are measured in joules
  • Energy is the ability to do work
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Gravitational Potential Energy

GPE = mass x gravitational field strength x height

Reminder: Gravitational field strength is the force per kilogram acting on an object    in a gravitational field

  • In order to lift an object you must apply enough force to overcome gravity
  • The force of gravity is called its weight and this is defined as:

weight = mass x gravitational field strength

  • The energy is stored as gravitational potential energy and it can be returned by releasing the object from its new position, thereby allowing gravity to do work on the object and causing it to speed up and gain kinetic energy
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Gravitational Potential Energy on a Roller Coaster

At the start of the ride, motors drag the cars to the top of the highest part of the ride.As this happens electrical energy becomes kinetic energy becomes GPE

As the car swoops down the track the GPE is converted to kinetic energy. It would continue to move around the track until it reached the highest point agian without needing more energy input - if energy was not converted ito otherforms along the way

As the car climbed to another high point it would slow down as its KE turned into GPE

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Kinetic Energy

Kinetic Energy =   ½mass x speed²


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Power

Power = Work Done ÷ Time Taken

  • Power is measured in watts if work done is measured in joules and time is measured in seconds
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