alleryStart learning →What happens to relativistic momentum, p = gamma m u, as an object's speed u approaches the speed of light c?
AIt approaches infinity
BIt approaches zero
CIt stays equal to mc
DIt becomes negative
Answer & Solution
Correct answer: A. It approaches infinity
1. Relativistic momentum is p = gamma m u, and gamma grows without bound as u approaches c.
2. Because gamma grows without bound, the momentum p also approaches infinity as u approaches c.
3. This is why an object with mass cannot actually reach the speed of light, since infinite momentum is not physically reasonable.
4. Momentum does not approach zero, stay fixed at mc, or turn negative as speed increases toward c.
5. So momentum approaching infinity is correct.
_Source: OpenStax Physics (CC BY 4.0), Ch 10 "Special Relativity", section 10.2 Consequences of Special Relativity_
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