### GCSE Physics Revision: Changes in Energy

#### 5th April 2017

New GCSE Science Revision and Learning

Changes in energy - key information to remember

Students need to be able to calculate changes in energy; whether it’s a moving object, a stretched back spring or an object falling from a height. This is a key part of the new GCSE science examinations.

To calculate the kinetic energy  of a moving object you have to use the equation:

• Kinetic energy = 0.5 x mass x (speed)2

Also written as…

• Ek = ½ m v2

Each of these variables is measured in a different way:

• Kinetic energy or Ek  is measured in joules or J

• Mass or m is measured in kilograms or kg

• Speed or v is measured in metres per second or m/s

To calculate how much elastic potential energy is stored in a stretched back string you have to use this equation:

• Elastic potential energy = 0.5 × spring constant × extension2

Also written as…

• Ee = ½ k e2

This is an equation that assumes the limit of proportionality has not been exceeded

Each of these variables is measured in a different way:

• Elastic potential energy or Ee is measured in joules or J

• Spring constant or k is measured in newtons per metre or N/m

• Extension or e is measured in metres or m

To calculate the gravitational potential energy of a raised object you have to use the equation:

• g . p . e . = mass × gravitational field strength × height

Also written as…

• Ep = m g h

Each of these variables is measured in a different way:

• Gravitational potential energy or Ep is measured in joules or J

• Mass or m is measured in kilograms or kg

• gravitational field strength or g is measured in newtons per kilogram or N/kg

• Height or h is measured in metres or m

Calculating the changes in energy of a moving object, a stretched back string and a raised object are simple once you’ve learnt all the key facts above. It can be easy to just memorise the equations but you have to remember the way the variables are measured as well. Why not changes in energy check out our song too! Learning this is very important for your future GCSE examinations.

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