Units (Forces and Motion)
2 marks · Normal(a)[2 marks]
A shopping trolley has a mass of 14 kg and is moving at 2 m/s. Calculate its momentum and give the correct SI unit.
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(a) momentum = 28 kg m/s
Also accept: 28 kg m/s
Common mistakes: using speed instead of mass or vice versa; wrong units
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Marking points
M1 (a) · 1 mark · Substitutes values correctly into the momentum equation, or shows momentum = mass × velocity. (follow-through)
A1 (a) · 1 mark · Correct final answer with correct SI unit (kg m/s or kg⋅m/s).
Worked solution
Momentum = mass × velocity
p = 14\ \mathrm{kg} \times 2\ \mathrm{m/s} = 28\ \mathrm{kg\ m/s}