Question

In Relativistic case, as the velocity of the particle approaches the speed of light, the Kinetic energy approaches ___________

(a) Zero

(b) Kinetic Energy as in Non-Relativistic case

(c) Rest Energy

(d) Infinite

This question was posed to me in a job interview.

This interesting question is from Mass Energy Relation topic in chapter Ultrasonics & Relativity of Engineering Physics I

Answer 1

The correct option is (d) Infinite

To explain I would say: In Relativistic case, the expression for Kinetic Energy is: Ek = \((\frac{m_0}{\sqrt{1-\frac{v^2}{c^2}}} – m_0)c^2\)

Thus, as v -> c, v/c -> 1.

Thus, the Kinetic Energy approaches infinity, which would require an infinite amount of external work.