Question

Four identical balls, $A,B,C$ and $D$ are placed on a smooth horizontal plane such that $B,C$ and $D$ are in one line and are in contact and $A$ is kept along the same line but a distance away. Now, $A$ is set in motion with speed $v$ along the line and it strikes the ball $B$. After this collision, which is elastic.

• A. Balls, $A,B,C$ will be at rest and $D$ will move with speed $v$
• B. $A$ will be at rest, where $B,C$ and $D$ will move together with speed $v/3$
• C. $A$ will rebound with speed $v/2$ while $B,C$ and $D$ will move together with speed $v/2$
• D. $A,B,C$ and $D$ will move together with speed $v/4$

Answer 1

The correct option is A Balls, $A,B,C$ will be at rest and $D$ will move with speed $v$

It is a case of elastic collision, whole of energy of $A$ is transferred to $D$.