Question 3:
The kinetic energy of an object of mass, m moving with a velocity of 5 m s−1 is 25 J. What will be its kinetic energy when its velocity is doubled? What will be its kinetic energy when its velocity is increased three times?
Answer:
Expression for kinetic energy is 
m = Mass of the object
v = Velocity of the object = 5 m s−1
Given that kinetic energy, EK = 25 J
(i) If the velocity of an object is doubled, then v = 5 × 2 = 10 m s−1.
Therefore, its kinetic energy becomes 4 times its original value, because it is proportional to the square of the velocity. Hence, kinetic energy = 25 × 4 = 100 J.
(ii) If velocity is increased three times, then its kinetic energy becomes 9 times its original value, because it is proportional to the square of the velocity. Hence, kinetic energy = 25 × 9 = 225 J.
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