Lesson 10 of 15

Relativistic Momentum

Relativistic Momentum

Classical momentum p=mvp = mv is not conserved in all inertial frames. The relativistic fix multiplies by γ\gamma:

p=γmv=mv1v2/c2p = \gamma m v = \frac{mv}{\sqrt{1 - v^2/c^2}}

where mm is the rest mass — an invariant property of the particle. At low speeds γ1\gamma \approx 1 and we recover pmvp \approx mv. As vcv \to c, pp \to \infty: no finite force can push a massive object to light speed.

Force and Momentum

Newton's second law keeps the same form in relativity: F=dp/dtF = dp/dt. But since p=γmvp = \gamma mv and γ\gamma itself depends on vv, the force needed to maintain constant acceleration grows without bound as vcv \to c.

Momentum Ratio

The ratio of relativistic to classical momentum is simply γ\gamma:

prelpclass=γ\frac{p_\text{rel}}{p_\text{class}} = \gamma

v/cv/cγ\gammaRatio
0.11.0050.5% correction
0.61.2525% correction
0.81.66767% correction
0.99≈7.09609% correction

Your Task

Implement relativistic_momentum(m, v) returning p=γmvp = \gamma mv, and momentum_ratio(v) returning γ\gamma — the factor by which relativistic momentum exceeds classical momentum. Use c=299792458.0c = 299792458.0 m/s defined inside each function.

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