Question

A body of mass $2$ kg moving with a velocity of $3$ m/sec collides head-on with a body of mass $1$ kg moving in opposite direction with a velocity of $4$ m/sec. After collision, two bodies stick together and move with a common velocity which in m/sec is equal to

• A. $1/4$
• B. $1/3$
• C. $2/3$
• D. $3/4$

Answer 1

Answer: (C)

$2/3$

Since There is no external force, we can apply momentum conservation,

Initial momentum of the system =$m_1{v}_1-m_2{v}_2$

$P_i=2\times 3-1\times 4=2kg.m/s$
As body sticks together $\therefore$ final momentum = $(m_1+m_2)V$
By conservation of momentum $(m_1+m_2)V=P_i$

$(2+1)\times V=2$

$V=\frac{2}{3}m/s$