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3 Conservation of energy

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Question 23

The electric motor of a laboratory centrifuge is supplied with 1.5 kJ of energy while the rotor speeds up. The efficiency of the motor is 60%. Its useful output is the energy transferred to the kinetic energy store of the rotor, and all of its other output is transferred to the surroundings. The energy stored in the motor itself does not change.

Four records of the motor's energy transfers are proposed.

RecordUseful transfer to rotor in kJ\mathrm{kJ}kJUnwanted transfers to surroundings in kJ\mathrm{kJ}kJ
10.900.60
20.600.90
30.901.50
42.501.00

Which record correctly represents the motor's energy transfers?

[1]
A

Record 1

B

Record 3

C

Record 4

D

Record 2

Markscheme

3 Conservation of energy Questions

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

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