Power

4 marks · Normal

A small electric motor raises a 2.0 kg mass vertically upwards a distance of 8.0 m in 6.0 s.

(a)

Calculate the work done by the motor in raising the mass.

[2 marks]

(b)

Calculate the power output of the motor during this time.

[2 marks]

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) 160 J

(b) 27 W

Common mistakes: Confusing mass with weight; Incorrect formula for power

Show mark scheme and worked solution

Marking points

M1 (a) · 1 mark · Correct application of W = mgh

A1 (a) · 1 mark · Correct final answer with unit (160 J)

M2 (b) · 1 mark · Correct substitution into P = W/t (using answer from (a)) (follow-through)

A2 (b) · 1 mark · Correct value for power with unit (27 W or correct follow-through) (follow-through)

Worked solution

a) Work done, W = mgh

b) Power, P = Work done / time