Q2 of 11 Page 84

Check whether the power marked in the motion used for pumping water from the well in your home and the power received during the working of it are equal, by considering the time taken to fill the tank and the height of the tank.

Power indicated on the motor = 441 J

The height of the tank from the ground is = 30 m


The volume of the tank is = 1500 L


Which implies, volume of the tank = 1500 kg


Work done by the motor to completely fill the tank


= Force applied × displacement of the object


= m × g × h (force = m × a = m × g)


= 1500 × 9.8 × 30


= 441000 J



Time taken to completely fill the water = 1000 s


Hence,


Power = 441000 / 1000


= 441 J


Hence our observation of the power used and the power indicated on the motor match.


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