Question

A body of mass $m$, is moving with velocity $\upsilon$. It collides with another stationary ball of mass $m_2$. They get embedded. At the point of collision, 'velocity' of the system will

• A. increase
• B. decrease but not to zero
• C. zero
• D. remain the same.

Answer 1

Answer: (B)

Just before the collision the velocity of the center of mass will be $u =$ $\frac{ m _{1} \times V + m _{2} \times 0}{ m _{1}+ m _{2}}=\frac{ m _{1}}{ m _{1}+ m _{2}} V$
after the collision if the system moves with velocity $V _{0}$ then on conserving the momentum
we will get $m _{1} V +0=\left( m _{1}+ m _{2}\right) V _{0}$
or $V _{0}=\frac{ m _{1}}{ m _{1}+ m -2} V$
we can notice that both $V _{0}$ and $u$ are same, due to absence of external force on the system.