Question

The diagram to the right shows the velocity-time graph for two masses $R$ and $S$ that collide elastically. Which of the following statements is true :
$\left(I\right)$ $R$ and $S$ moved in the same direction after the collision
$\left(II\right)$ Kinetic energy of the system $\left(RandS\right)$ is minimum at $t=2$ milli sec.
$\left(III\right)$ The mass of $R$ is greater than the mass of $S$.

• A. $I$ only
• B. $II$ only
• C. $I$ and $II$ only
• D. $I,II$ and $III$

Answer 1

Answer: (D)

$I,II$ and $III$

$\left(I\right)$ both of them moved in same direction as final velocity of both of them is positive.
$\left(II\right)$ Kinetic energy if function of $v^2$ and will be minimum at the instant when both are on same speed.
$\left(III\right)$Momentum will be conserved, as in the graph R drops less velocity as compared to rise in S's velocity for same amount of momentum transferred so R is heavier than S.
So, all the statements are correct.