Two blocks of 8 kg and 4 kg are connected by a spring on a frictionless surface. An impulse gives the 8 kg block speed 6 m/s while the other is initially at rest. Find centre-of-mass speed (m/s).
Physics · Mixed Chapter
JEE Main Practice

Question

Two blocks of 8 kg and 4 kg are connected by a spring on a frictionless surface. An impulse gives the 8 kg block speed 6 m/s while the other is initially at rest. Find centre-of-mass speed (m/s).

G1 Physics · Accepted Answer

Step 1: Total momentum immediately after the impulse p=8×6+4×0=48 kg·m/s. Step 2: Total mass M=8+4=12 kg. Step 3: v_cm=p/M=48/12=4 m/s.