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Question
(a) Define power and name its unit.
(b) A girl weighting 50 kg climbs up 60 steps each of 20 cm height in 5 minutes. Calculate the power developed.
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Solution
(a) The rate of doing work is called power.
SI unit of power = watt
CGS unit of power = erg per second
(b) Given mass = 50kg
Total height traveled = 60 x 20 cm = 1200 cm = 12m
g = 10 ms-2
time taken = 5 min = 5 x 60 s = 300 s
Work done = mgh = 50 x 10 x 12 = 6000J
Power = `"work done"/"time taken" = 6000/300` = 20 watt
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