# The boy lifted a stone weighing 2kg to a height of 60cm. what work did he do?

The boy lifted a stone weighing 2kg to a height of 60cm. what work did he do? calculate the power that the boy developed if he lifted the stone 0.2s.

Data: mk – the mass of the stone raised by the boy (mk = 2 kg); Δh – change (increase) in the height of the stone (h = 60 cm; in the SI system h = 0.6 m); t – the duration of the rise of the stone (t = 0.2 s).

Const: g – acceleration due to gravity (g ≈ 9.8 m / s2).

1) The work done by the boy: Amech = ΔEp = mk * g * Δh = 2 * 9.8 * 0.6 = 11.76 J.

2) Boy’s power: N = Amech / t = 11.76 / 0.2 = 58.8 W.

Answer: The boy’s work is 11.76 J, the power is 58.8 W.

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