A block of mass m moving with speed v collides with another block of mass 4m at rest. The lighter block comes to rest after the collision. Find the coefficient of restitution.
Physics · Mixed Chapter
JEE Main Practice

Question

A block of mass m moving with speed v collides with another block of mass 4m at rest. The lighter block comes to rest after the collision. Find the coefficient of restitution.

G1 Physics · Accepted Answer

Step 1: Along the collision line, let final velocities be v₁ = 0 for mass m and v₂ for mass 4m. Step 2: Linear momentum conservation: mv = m(0) + 4mv₂. Step 3: Hence v₂ = v/4. Step 4: Coefficient of restitution e = (relative speed of separation)/(relative speed of approach) = (v₂ − v₁)/(v − 0). Step 5: e = (v/4)/v = ¼ = 0.25. Final answer: 0.25.