Three identical spherical balls $A, B$ and $C$ are placed on a table as shown in the figure along a

Question

Three identical spherical balls $A, B$ and $C$ are placed on a table as shown in the figure along a straight line. $B$ and $C$ are at rest initially. The ball $A$ hits $B$ head on with a speed of $10 \mathrm{~m} \mathrm{~s}^{-1}$. Then after all collisions (assumed to be elastic) $A$ and $B$ are brought to rest and $C$ takes off with a velocity of....

Professor PC Thomas Classes · Answer

Since $A, B$ and $C$ are identical balls, if any of the two balls undergo elastic collision, they will exchange their velocities. Thus, when $A$ and $B$ collide, $A$ comes to rest, and $B$ start moving ahead with $10 \mathrm{~m} \mathrm{~s}^{-1}$. Similarly, when $B$ collides with $C, B$ comes to rest and $C$ starts moving ahead with a speed of $10 \mathrm{~m} \mathrm{~s}^{-1}$.