IGCSE Physics: Energy, Work and Power Questions
Energy questions are formula driven, so the marks come from choosing the right equation and units. These worked examples cover work done, power and gravitational potential energy.
What you need to know
- Work done equals force times distance moved in the direction of the force, measured in joules.
- Power equals work done, or energy transferred, divided by time, measured in watts.
- Gravitational potential energy equals mass times gravitational field strength times height, mgh.
- Energy is conserved: it is transferred between stores, never created or destroyed.
Practice questions with answers
A force of 50 N moves an object 3 m in the direction of the force. Calculate the work done.
Work done = force times distance = 50 times 3 = 150 J.
A motor transfers 600 J of energy in 30 seconds. Calculate its power.
Power = energy transferred divided by time = 600 divided by 30 = 20 W.
Calculate the gravitational potential energy gained by a 2 kg mass lifted 5 m. (g = 10 N/kg)
Gravitational potential energy = mass times g times height = 2 times 10 times 5 = 100 J.
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What is the formula for work done?
Work done equals force times distance moved in the direction of the force. It is measured in joules.
What is the difference between energy and power?
Energy is the total amount transferred, in joules. Power is the rate of transfer, energy per second, in watts.
How do you calculate gravitational potential energy?
Multiply mass by gravitational field strength by height, mgh. With g at about 10 N/kg for IGCSE.
Is energy ever lost?
Energy is never destroyed. It is conserved, but some is often transferred to less useful stores such as heat, so it is described as dissipated.