Elastic Collision Calculator
🎱 Momentum & collisions. Use the Elastic collision (target at rest) formula to find ball 1 afterwards, mass 1, mass 2, ball 1 before: pick the value you want, type the others, and the answer updates as you go.
Solves for the first ball’s velocity afterwards; equal masses → it stops.
Pick the ○ next to the value you want to find, fill in the others, and it solves as you type.
What each letter means
| Quantity | Unit |
|---|---|
| Ball 1 afterwards | m/s |
| Mass 1 | kg |
| Mass 2 | kg |
| Ball 1 before | m/s |
Worked example
Find the ball 1 afterwards when Mass 1 = 0.16 kg, Mass 2 = 0.16 kg, Ball 1 before = 4 m/s.
Using v1' = (m1 - m2)/(m1 + m2) u1, v2' = 2m1/(m1 + m2) u1: Ball 1 afterwards = 5.839 × 10⁻¹⁰ m/s.
Frequently asked questions
What is the formula for Elastic collision (target at rest)?
v1' = (m1 - m2)/(m1 + m2) u1, v2' = 2m1/(m1 + m2) u1. Solves for the first ball’s velocity afterwards; equal masses → it stops.
What do the letters stand for, and what units are used?
Ball 1 afterwards in m/s, Mass 1 in kg, Mass 2 in kg, Ball 1 before in m/s.
How do you calculate ball 1 afterwards?
Put the values into v1' = (m1 - m2)/(m1 + m2) u1, v2' = 2m1/(m1 + m2) u1. For example, with Mass 1 = 0.16 kg, Mass 2 = 0.16 kg, Ball 1 before = 4 m/s, ball 1 afterwards = 5.839 × 10⁻¹⁰ m/s.
Can I solve for a different value?
Yes. In the calculator above, pick the circle next to any value (ball 1 afterwards, mass 1, mass 2, ball 1 before) and fill in the others: it rearranges the formula for you.
