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Question
Calculate the power of a crane in watts, which lifts a mass of 100 kg to a height of 10 m in 20s.
Solution
According to the problem, mass = m= 100 kg height = h – 10 m, time interval, t = 20 s. Power is the rate of doing work with respect to time.
We know from the formula that, the power = work done/time = `(Fds cos θ)/(time)`
F = mgh
mg = 100 × 10 = 1000
h = 10 m
t = 20s
θ = 0, as the force and the displacement, are in the same direction.
Hence power = `(1000 xx 10 cos 0)/20` = 500 watts
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