question_answer

A moving body of mass m and velocity 3 km/h 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    [CBSE PMT 1996; JIPMER 2001, 02]

A)             3 km/h

B)               2 km/h

C)             1 km/h

D)               4 km/h

Correct Answer: C

Solution :

    Initial momentum = \[m\times 3+2m\times 0=3m\] Final momentum = \[3m\times V\] By the law of conservation of momentum \[3m=3m\times V\]Þ \[V=1\ km/h\]