Power
3 marks · NormalA student with a mass of 60 kg runs up a flight of stairs in 9.0 s. The stairs have 12 steps, each 0.25 m high. Use g = 10 N/kg.
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200 W (±5)
Common mistakes: Incorrect calculation of total height; Using mass instead of weight
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Marking points
M1 · 1 mark · Correctly calculates total height climbed (12 × 0.25 = 3.0 m)
M2 · 1 mark · Calculates work done (W = mgh = 60 × 10 × 3.0 = 1800 J) (follow-through)
A1 · 1 mark · Calculates power (P = W / t = 1800 / 9.0 = 200 W) (follow-through)
Worked solution
Total height climbed = 12 × 0.25 m = 3.0 m