Question

A running man has half the kinetic energy of that of a boy of half of his mass. The man speeds up by \(1\ \text{m/s}\) so as to have the same kinetic energy as that of the boy. The original speed of the man is

• A. \((\sqrt{2} - 1)\ \text{m/s}\)
• B. \(\sqrt{2}\ \text{m/s}\)
• C. \(\frac{1}{\sqrt{2} - 1}\ \text{m/s}\)
• D. \(\frac{1}{\sqrt{2}}\ \text{m/s}\)

Hint:

Rationalize: \(\frac{1}{\sqrt{2}-1} = \sqrt{2}+1 \approx 2.414\ \text{m/s}\).

Answer 1

The Correct Option is C