Question

A boy of mass 40kg climbs up the stairs and reaches the roof at a height 8m in 5 s. Calculate:

(i) The force of gravity acting on the boy,

(ii)The work done by him against gravity,

(iii)The power spent by the boy.

(take g= 10ms-2)

Answer 1

Answer:

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Answer 2

Given :-

• Mass of a boy = 40 kg

• Vertical height moved by a boy, h = 8 m

• Time taken by a boy, t = 5 s

(i) Force of gravity acting on the boy

• F = mg
• = 40 × 10

• = 400 N

(ii) Work done by a boy against the force of gravity while climbing,

• Work done by a boy = Force × distance moved in the direction of force

• W = F × S

• W = 400 × 8

• W = 3200 J

(iii) Power spent = (work done / time taken)

• = 3200 / 5

• = 640 W