(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.