Energy Transfers
3 marks · EasyA student rubs their hands together on a cold day.
Describe the main energy transfer that occurs while rubbing hands.
Which energy store increases as the hands become warmer?
Explain why rubbing hands is not 100% efficient.
Work this out on paper, then compare with the answer and worked solution below. With a free account you can submit written answers for marking.
Show answer
(a) Movement energy is transferred to heat (thermal energy) by friction.
(b) Thermal energy store (of the hands) increases.
(c) Some energy is transferred to the surroundings and as sound, not only to warming the hands.
Show mark scheme and worked solution
Marking points
B1 (a) · 1 mark · Describes movement (kinetic) energy converted to heat (thermal energy) by friction.
B1 (b) · 1 mark · Identifies the thermal energy store of the hands increases.
B1 (c) · 1 mark · Explains not all energy goes to heating hands; some is lost to sound/air/surroundings.
Worked solution
a. The movement energy (kinetic energy) of the hands is transferred to heat (thermal) energy by friction.
b. The thermal energy store of the hands increases.
c. Not all energy goes into warming the hands; some is lost as sound and to the air.