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Question
A boy of mass 40 kg climbs up the stairs and reaches the roof at at height 8 m in 5s.Calculate:
(i) the force of gravity acting on the boy,
(ii) the work done by him against the force of gravity,
(iii) the power spent by the boy.
(Take g=10 m s−2).
A boy of mass 40 kg climbs up the stairs and reaches the roof at at height 8 m in 5s.Calculate:
(i) the force of gravity acting on the boy,
(ii) the work done by him against the force of gravity,
(iii) the power spent by the boy.
(Take g=10 m s−2).
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Solution
Mass of boy = 40 kg Vertical height moved, h = 8m Time taken, t = 5s.
(i) Force of gravity on the boy F = mg = 40 × 10 = 400N
(ii) While climbing, the boy has to do work against the force of gravity.
Work done by the boy in climbing= Force × distance moved in the direction of force Or,
W = F x S= 400 x 8= 3200 J
(iii) Power spent =
(i) Force of gravity on the boy F = mg = 40 × 10 = 400N
(ii) While climbing, the boy has to do work against the force of gravity.
Work done by the boy in climbing= Force × distance moved in the direction of force Or,
W = F x S= 400 x 8= 3200 J
(iii) Power spent =
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