Q. 38

# A raindrop of mass 1.00 g falling from a height of 1 km hits the ground with a speed of 50 m s–1. Calculate

(a) the loss of P.E. of the drop.

(b) the gain in K.E. of the drop.

(c) Is the gain in K.E. equal to loss of P.E.? If not why.

Take g = 10 m s^{-2}

Answer :

Mass m of drop = 1g = 0.001 kg

Change in height Δ h = 1 km = 1000 m

Final velocity = 50

∵ the drop starts from rest, initial velocity = 0

∴ initial K.E = 0 J

And final K.E =

a) Loss in P.E. =

b) Gain in K.E.

c) No, the gain in K.E. equal to loss of P.E. is not the same because of resistance like drag and viscous force against the drop.

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