Inelastic collision
A 0.40 kg cart moving at 3.0 m s⁻¹ collides with a stationary 0.60 kg cart. The carts stick together after the collision.
Calculate:
a) their common speed after the collision;
b) the kinetic energy lost during the collision.
Worked answer
Solution
- Step 1
Apply conservation of momentum:
0.40 × 3.0 = (0.40 + 0.60)v. - Step 2
v = 1.20 m s⁻¹. - Step 3
Initial kinetic energy:
1/2 × 0.40 × 3.0² = 1.80 J. - Step 4
Final kinetic energy:
1/2 × 1.00 × 1.20² = 0.72 J. - Step 5
Energy lost:
1.80 - 0.72 = 1.08 J.
Final answer
Common speed = 1.20 m s⁻¹; kinetic energy lost = 1.08 J.
Common mistake
Assuming kinetic energy is conserved in a perfectly inelastic collision.
Concepts tested
- conservation of momentum
- inelastic collision
- kinetic energy
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