Momentum & Collision · Interactive

Collision Lab

Two carts collide on a frictionless track. Total momentum is always conserved — but kinetic energy survives only when the collision is perfectly elastic. Watch the green centre-of-mass marker glide through the whole event at one unchanging speed.

■ Cart 1 velocity ■ Cart 2 velocity ▲ Centre of mass Frictionless track · walls at both ends

Setup

Mass m₁ 2.0 kg
Mass m₂ 3.0 kg
Velocity v₁ 4.0 m/s
Velocity v₂ -2.0 m/s
Restitution e 1.00
Elastic
Collision type
2.0
momentum p (kg·m/s)
28.0
KE before (J)
28.0
KE after (J)
0.0
ΔKE (J)
p = m₁v₁+m₂v₂ conserved KE conserved iff e=1 v_cm constant

Playback

Try this: set e = 0 — the carts stick together and KE drops sharply (yet p and v_cm hold). Or give both carts equal mass with e = 1 head-on: they simply swap velocities.