Question

A man flies past a woman at a speed near the speed of light. What might correctly be said by whom as the man flies by? Assume that neither the man nor the woman usually travels so fast relative to other near-by objects

• A. The man could say, "I am more massive than usual"
• B. The man could say, "Time is passing more slowly for me the usual"
• C. The woman could say to the man, "You are more massive than usual"
• D. The woman could say to the man, " You are wider than usual"
• E. The woman could say, "Time is passing more quickly for me than usual"

Answer 1

The correct option is C The woman could say to the man, "You are more massive than usual"

Mass of the moving man as seen by the woman in rest frame $m=\frac{m_o}{\sqrt{1-v^2/c^2}}$ $⟹m>m_o$

where $m_o$ is the rest mass of the man.

Thus according to the woman, the man seems to be more massive than usual.