Question

When we are moving at a speed of light , Why the mass of a body changes?​

Answer 1

That is why all the particles that move at thespeed of light (e.g. photons) have zero restmass. As a particle with mass approaches the speed of light, its energy increases and becomes infinite at the speed of light, which is the reason why it can never be accelerated to reach that speed

Answer 2

Explanation:

Because our total energy is consumed when we are travelling at speed of light and our mass becomes zero