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A body is falling freely from rest from a height of 100m. The ratio of kinetic energy after 2 and 5 seconds is _____(a) 2:5(b) 4:25(c) 25:4(d) 5:2This question was posed to me in quiz.This question is from Kinetic Energy topic in section Work, Energy and Power of Physics – Class 11

Answer»

The CORRECT option is (b) 4:25

Easiest EXPLANATION: From newtons law;

v1 = u + gt1

v1 = 2g

v2 = u + gt2

v2 = 5g

KE1 : KE2 = v1^2 : v2^2

 = 4 : 25.



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