What is the conservation of momentum?

The law states that the total linear momentum of an isolated system remains constant. For a two-object collision: m1·v1 + m2·v2 = m1·v1' + m2·v2' (elastic) or (m1+m2)·vf (perfectly inelastic).

What is the difference between elastic and inelastic collisions?

In an elastic collision both momentum and kinetic energy are conserved; the objects bounce off each other. In a perfectly inelastic collision the objects stick together — momentum is conserved but kinetic energy is not (some converts to heat, sound, or deformation).

What sign convention is used for velocity?

Positive values mean motion to the right; negative values mean motion to the left. You can enter negative velocities for objects moving in the opposite direction.

What units should I use?

Mass can be in kilograms (kg) or any consistent unit. Velocity can be in m/s, km/h, or any consistent unit. The tool is unit-agnostic — just keep both masses in the same unit and both velocities in the same unit.

Can I use grams instead of kilograms?

Yes. As long as both masses use the same unit the results are correct. For example, enter mass in grams and velocity in cm/s and the output will also be in cm/s.

What if one object is stationary?

Set its initial velocity to 0. This is a common scenario — a moving object striking a stationary target.

Conservation of Momentum Calculator

Name: Conservation of Momentum Calculator
Availability: InStock
Author: Nham Vu

Enter the masses and initial velocities of two objects to find their post-collision velocities for elastic or perfectly inelastic collisions.

Collision Parameters

Object 1

Mass (m₁)

Velocity (v₁)

m/s

Object 2

Mass (m₂)

Velocity (v₂)

m/s

Collision Type

Elastic Perfectly Inelastic

Formulas Used

Elastic Collision

v1' = (m1 - m2)·v1 + 2·m2·v2) / (m1 + m2)

v2' = (2·m1·v1 + (m2 - m1)·v2) / (m1 + m2)

Enter masses and velocities, then click Calculate

Summary

Enter the masses and initial velocities of two objects to find their post-collision velocities for elastic or perfectly inelastic collisions.

How it works

Enter the mass of Object 1 (m1) and its initial velocity (v1).
Enter the mass of Object 2 (m2) and its initial velocity (v2).
Choose the collision type: Elastic or Perfectly Inelastic.
Click "Calculate" to see the final velocities and kinetic energy summary.
Use the Reset button to clear all fields and start a new calculation.

Use cases

Solve physics homework problems on 1-D collisions.
Verify hand calculations for elastic billiard-ball collisions.
Explore how mass ratio affects energy transfer in collisions.
Demonstrate Newton's cradle behavior with equal masses.
Analyze perfectly inelastic car crash scenarios for physics class.
Check momentum conservation in lab experiment data.

Frequently Asked Questions

Last updated: 2026-06-10 · Reviewed by Nham Vu