Question

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 1

Expression for kinetic energy is

m = Mass of the object

v = Velocity of the object = 5 m s⁻¹

Given that kinetic energy, = 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.