Question

A 3.0-kg block moving to the right on a frictionless table at 4.0 m/s makes a head-on collision with another 3-kg block moving 5 m/s to the left. Find the final velocity of the blocks, if the collision is PERFECTLY INELASTIC.

Answer 1

$m_1 = 3 \; kg \\ m_2 = 3 \; kg \\ u = 4 \; m/s \\ v = 5 \; m/s$

By momentum conservation:

$3 \times 4 -3 \times 5 = (3+3)v_f \\ v_f = -0.5 \; m/s$