Question

If the direction of velocity is changed by 180o simultaneously, the mass would _____________

(a) Change simultaneously

(b) Not Change

(c) Increase

(d) Decrease

The question was posed to me in an international level competition.

Enquiry is from Mass Variation with Velocity in chapter Ultrasonics & Relativity of Engineering Physics I

Answer 1

The correct answer is (b) Not Change

The explanation is: As we know, the relation for mass variation with velocity is m = \(\frac{m_0}{\sqrt{1-\frac{v^2}{c^2}}}\).

As we can see, it depends on the square of the velocity. Thus, changing the direction of velocity would not effect it.