Interactive collision lab: cart A rolls into cart B on a track, with ticker-tape dots and momentum arrows comparing total momentum before and after the collision
Bounce, stick or stall: the momentum total never budges
Roll a 0.50 kg cart into a second cart on a track and almost everything changes: speeds, directions, even how much kinetic energy survives. One number does not. Load cart B with masses, pick a bumper type, and compare the momentum arrows before and after.
Collision labStick · mB 0.75 kg
Set the mass of cart B · pick a bumper · each run replays the crash
p before 0.300 · p after 0.300 kg m/s
Mass of cart B0.75 kg
0.25 kg0.500.751.001.251.50 kg
Total p before
0.300
kg m/s · KE 0.090 J
Total p after
0.300
kg m/s · KE 0.036 J
Know This
With no external net force, total momentum before equals total momentum after in every collision, even when kinetic energy is lost.