(a) State and define SI unit of power.

(b) A person carrying 10 bricks each of mass 2.5 kg on his head moves to a height 20 m in the 50s. Calculate power spent in carrying bricks by the person (g = 10 m/s2)

(a) The rate of doing work is called as the power. The SI unit of power is Watt denoted by W.

1 Watt is the power of appliances that consume the energy at the rate of 1 joule per second.


(b) Given


Mass of brick = 2.5 kg


Weight = mg = 2.5×10 = 25 N


Weight of 10 bricks = 25×10 = 250 N


Height (h) = 20 m


Time (t) = 50 s


Power =


Power =



Power spent in carrying bricks is 100 Watt.


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