According to Einstein's theory of special relativity, the mass of an object moving at a speed close to that of light
Correct answer: B. increases relative to an observer at rest
- A. decreases
- B. increases relative to an observer at rest
- C. stays exactly the same
- D. becomes zero
Explanation
The relativistic factor grows without limit as the speed approaches c, so the effective mass rises and an infinite force would be needed to reach the speed of light, which is why no massive object can attain it. The effect is negligible at everyday speeds, which is why Newtonian mechanics works so well. Length contraction and time dilation follow from the same factor.
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