Consider a drop of rain water having mass 1 g falling from a height of 1 km . It hits the ground with a…

Consider a drop of rain water having mass 1 g falling from a height of 1 km. It hits the ground with a speed of 50 m s-1. Take g constant with a value 10 m s-2. The work done by the (i) gravitational force and the (ii) resistive force of air is
  1. i-10 Jii-8.25 J
  2. i 1.25 Jii-8.25 J
  3. i 100 Jii 8.75 J
  4. i 10 Jii-8.75 J

Solution

By Work-Energy Theorem
Wg+Wa=Kf-Ki
mgh+Wa=12mv2-0
10-3×10×103+wa=12×10-3×502
Wa= -8.75 J
work done due to gravity =mgh
= 10 3 ×10× 10 3
=10J

Asked in: NEET 2017

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