Two solid rubber balls $A$ and $B$ having masses $200$ and $400\, gm$ respectively are moving in opposite directions with velocity of $A$ equal to $0.3 \,m/s$. After collision the two balls come to rest, then the velocity of $B$ is .............. $\mathrm{m} / \mathrm{s} $

A ball of mass $10\, kg$ is moving with a velocity of $10\, m/s$. It strikes another ball of mass $5\, kg $ which is moving in the same direction with a velocity of $4 \,m/s$. If the collision is elastic, their velocities after the collision will be, respectively

Which one of the following statements does not hold good when two balls of masses $m _1$ and $m _2$ undergo elastic collision

A body of mass $1\,kg$ collides head on elastically with a stationary body of mass $3\,kg$. After collision, the smaller body reverses its direction of motion and moves with a speed of $2\,m / s$. The initial speed of the smaller body before collision is $..........ms ^{-1}$

In the elastic collision of objects

It is found that if a neutron suffers an elastic collinear collision with deuterium at rest, fractional loss of its energy is $p_d $ ; while for its similar collision with carbon nucleus at rest, fractional loss of energy is $P_c$. The values of $P_d$ and $P_c$ are respectively