Question

A moving body of mass m and velocity 3 km/hour collides with a rest body of mass 2m and sticks to it. Now the combined mass starts to move. What will be the combined velocity?

(a) 3 km/hour

(b) 4 km/hour 

(c) 1 km/hour

(d) 2 km/hour.

Answer 1

Correct option (c) 1 km/hour

Explanation:

Mass of body (m₁) = m; Velocity of first body (u₁) = 3 km/hour; Mass of second body in rest (m₂) = 2m and velocity of second body (u₂) = 0. After combination, mass of the body

M = m+2m = 3m

From the law of conservation of momentum, we get