Question

A block of mass m moving with a velocity v collides with another block of mass M at rest. The two blocks stick together due to the collision. The loss of K.E. expressed as a fraction of total initial kinetic energy is

(1) M/m+M

(2) m/M+m

(3) M²/m+M

(4) M-m/m+M

Answer 1

(1) M/m+M

Using principle of momentum conservation; the velocity of the composite block is given by

mv = (m + M) V

[∵ The momentum remains the same]