Question

Three particles $A,B$ and $C$ of equal mass move with equal speed $V$ along the medians of an equilateral triangles as shown in the figure. They collide at the centroid $G$ of the triangle. After the collision, $A$ comes to rest, $B$ retraces its path with the speed $V$. What is the velocity of $C$?

Answer 1

Initially all velocities are at ${120}^o$, and hence there resultant is .

That is velocity of CM is 0.

After collision at G-

$v_A=0$,

$v_{CM}=0$

$⟹v_B+v_C=0$

$⟹v_C=-v_B=-V$

Hence velocity of C is also $V$ but opposite to that of B after collision, that is along $\overrightarrow{BG}$.