Physics · Momentum

Momentum & 1D collision calculator

Compute final velocities, momentum balance, and kinetic energy loss for 1D collisions (elastic, perfectly inelastic, or coefficient e).

All calculations run locally in your browser; no data leaves this page.

How to use (3 steps)

  1. Pick a collision type: elastic (e = 1), perfectly inelastic (stick together), or inelastic with your own e.
  2. Enter masses and initial velocities u₁ and u₂. Use negative values to show the opposite direction on the 1D line.
  3. Press Compute to get v₁, v₂, momentum and energy before/after, then copy the URL to share the setup.

Default example: m₁ = 1 kg, u₁ = 3 m/s, m₂ = 2 kg, u₂ = 0 m/s, elastic. It auto-computes on load so you can see the result instantly.

Inputs

Use kg and m/s. This calculator keeps the sign of each velocity; rightward is positive by convention.

Elastic: e = 1.0 (fixed).
kg
m/s
kg
m/s

Use positive/negative values to show direction along the line (rightward is positive).

Results

How it is calculated

    FAQ

    What is the difference between elastic and inelastic collisions?

    Elastic collisions conserve both momentum and kinetic energy (e = 1). Inelastic collisions conserve momentum but lose some kinetic energy. In a perfectly inelastic collision the objects stick together and move with one final speed.

    Can I enter negative speeds?

    Yes. Set rightward as positive on the 1D line. A negative value means the object travels to the left, and the calculator keeps that sign when summing momentum.

    What does the coefficient of restitution e mean?

    It is the ratio of relative speed after impact to relative speed before impact. e = 1 is perfectly elastic, e = 0 is perfectly inelastic, and values between 0 and 1 describe partially elastic collisions.

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