A boy of mass 50 kg climbs 43 steps in 10 s. If each step is 15 cm high, find his power. Take \(g = 10 \text{ ms}^{-2}\).
322.5 W
Total vertical height = 43 × 0.15 = 6.45 m.
Work done against gravity = mgh = 50 × 10 × 6.45 = 3225 J.
Power = work/time = 3225 / 10 = 322.5 W.
Note the unit — power is measured in watts (J/s).
Hence, 322.5 W.
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Express the power dissipated in a 100 Ω resistor in dB relative to 1 mW, when the voltage across the resistor is 1.0 Vrms
An elevator weighing 500 kg is to be lifted up at a constant velocity of 0.25 m/s. What would be the minimum horsepower of the motor to be used? G = 9.8 m/s2 and there is no frictional loss.
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How many units of electric power will be consumed by 4 motors of 0.5 HP each in 8 hours?
The power of a water pump is 2 kW. The amount of water (in litres) it can raise in one minute to a height of 10 m will be :
(g = 10 m/s 2 )
