NEET2017Physics-Work, Energy and Power
NEET 2017 Physics Work Done by Forces MCQ Question
Type: MCQ-numerical-Medium-Class 11
Consider a drop of rain water having mass 1g falling from a height of 1 km. It hits the ground with a speed of 50 m/s. Take ‘g’ constant with a value 10 m/s². The work done by the (i) gravitational force and the (ii) resistive force of air is:
A
(i) –10 J (ii) –8.25 J
B
(i) 1.25 J (ii) –8.25 J
C
(i) 100 J (ii) 8.75 J
D
(i) 10 J (ii) –8.75 J
Correct Answer
Option D
Detailed Explanation
The work done by gravitational force is mgh = 0.001 kg × 10 m/s² × 1000 m = 10 J. The kinetic energy at impact is 0.5 × 0.001 kg × (50 m/s)² = 1.25 J. The work done by air resistance is the difference: 10 J - 1.25 J = 8.75 J (negative because it opposes motion).
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