Diagram shows v-t graph for two masses R and S that collided elastically. Show that....

1)R and S move in same direction after collision.

2)KE of system is minimum at t=2millisec.

3)mass of R > mass of S.

dear student,
RandSboth have positive velocity after the collision, hence they are moving in the same direction.
At the midpoint of the collision both the velocity-time curves intersect. Hence they have the same velocity at the mid time of the collision.
After the collision,Rhas a lesser velocity, hence it has a higher mass in order to keep the momentum conserved.
thank you.