Perfectly inelastic collision
A 2 kg cart moving at 3 m/s collides with and sticks to a stationary 1 kg cart. What is their speed just after the collision?
Answer C: explanation for every choice
A
At 1 m/s the total momentum would be 3 kg·m/s, only half the initial 6 kg·m/s.
B
This averages the two velocities instead of conserving momentum.
C
Correct. Momentum is conserved: 2 × 3 = (2 + 1)v, so v = 2 m/s.
D
Keeping the original speed with more total mass would increase momentum, which cannot happen.
TakeawayMomentum is conserved in all collisions. Kinetic energy is lost in inelastic ones.
Equation usedMomentum and impulse
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