1.

A ball of mass 200g falls from a height of 5 meters. What is its kinetic energy when it just reaches the ground?

Answer»

Mass = 200 g = 0.2kg 

Height = 5m 

Initial velocity, u = 0

Acceleration due to gravity, g = 9.8 m/s2 

Final velocity, v

Using third equation of motion, 

v2 – u2 = 2gs 

v2 = 98 

Kinetic energy = ½ mv2 

Kinetic energy = (½)(0.2)(98) = 9.8J



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