A 2.0-kg cart moving at 4.0 m/s collides with a stationary 3.0-kg cart. The two carts stick together after the collision. What is the velocity of the combined mass immediately after the collision?
A1.6 m/s
B2.0 m/s
C4.0 m/s
D6.7 m/s
Explanation
📌 Conservation of momentum (perfectly inelastic): m₁v₁ + m₂v₂ = (m₁+m₂)v_f. (2.0)(4.0) + 0 = (5.0)v_f → v_f = 1.6 m/s. Distractor B averaged velocities without mass weighting; C ignored mass conservation; D used wrong combined mass. Note: kinetic energy is NOT conserved here — 15 J is lost to heat, sound, and deformation.