Units (Forces and Motion)
2 marks · Exam LevelA student writes the following physical quantity and its unit: 'momentum: newton (N)'. Identify the mistake, and state the correct SI unit and symbol for momentum.
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The mistake is that the unit newton (N) is incorrect for momentum. The correct SI unit and symbol for momentum is kilogram metre per second (kg m/s).
Also accept: The correct unit is kg m/s; momentum is not measured in newtons
Common mistakes: Using newton (N) for momentum; Giving newton metre (Nm)
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Marking points
B1 · 1 mark · Identifies that newton (N) is not the correct SI unit for momentum
B2 · 1 mark · Gives the correct SI unit and symbol for momentum (kg m/s)
Worked solution
The student's mistake is using newton (N) as the unit for momentum. The correct SI unit for momentum is kilogram metre per second (kg m/s).