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=mv1−v2/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 γ≈1\gamma \approx 1 and we recover p≈mvp \approx mv. As v→cv \to c, p→∞p \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 v→cv \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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