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3 Conservation of energy

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Question 45
F

An electric motor is used to lift a crate onto the roof of a building.

The motor is supplied with 5000 J of energy. The crate has a mass of 20 kg and is lifted through a height of 15 m.

Gravitational field strength (ggg) = 10 N/kg

a.

Calculate the energy transferred to the gravitational potential energy store of the crate.

[2]
b.

Calculate the efficiency of the motor.

[2]
c.

The motor becomes hot while it is lifting the crate.

Explain why.

[2]
d.

The motor is switched off and cools down.

Describe what happens to the energy in the thermal store of the motor.

[2]
Markscheme

3 Conservation of energy Questions

  1. GCSE
  2. /Physics
  3. /3 Conservation of energy

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