Inelastic Collision Calculator
Works out the result of a collision that loses energy.
After the collision
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Share sends a link that reopens these numbers. Copy details pastes the full breakdown as a list.
Mass 1 velocity after —
Mass 2 velocity after —
Kinetic energy lost —
Share of the energy lost — %
Total momentum — kg·m/s
Assumes —
The formula
stuck together: v = (m₁u₁ + m₂u₂) ÷ (m₁ + m₂) v₁ = (p − m₂e(u₁ − u₂)) ÷ (m₁ + m₂) v₂ = (p + m₁e(u₁ − u₂)) ÷ (m₁ + m₂)
Momentum is conserved. Kinetic energy is not, and e sets how much of the closing speed returns as separating speed.
What to watch out for
Leave the restitution at zero for objects that stick, such as a car crash where the vehicles lock together.
Frequently Asked Questions
What is the final speed when a 2 kg mass at 3 m/s hits and sticks to a still 1 kg mass?
2 m/s, losing 3 J of 9 J.
Is momentum still conserved?
Yes, as long as no outside force acts during the collision. Only kinetic energy is lost.