Four smooth steel balls of equal mass at rest are free to move along a straight line without friction. The first ball is given a velocity of $0.4 \,m/s$. It collides head on with the second elastically, the second one similarly with the third and so on. The velocity of the last ball is .......... $m/s$

Three different projectiles, each with the same mass, are fired with speed $v$ at a wall. In case $A,$ the projectile bounces straight back with speed $v.$ In case $B$, the projectile sticks to the wall. In case $C$, the projectile crashes through the wall and emerges with half its original speed. These three cases are shown here.

Place the impulse exerted by the wall on the projectile in each of these three cases in the correct order.

Two equal masses ${m_1}$ and ${m_2}$ moving along the same straight line with velocities $+ 3 \,m/s$ and $-5\, m/s$ respectively collide elastically. Their velocities after the collision will be respectively

$A$ bal $A$ collides elastically with another identical ball $B$ initially at rest $A$ is moving with velocity of $10m/ s$ at an angle of $60^o$ from the line joining their centres. Select correct alternative :

Two masses of $0.25\, kg$ each moves towards each other with speed $3\, ms^{-1}$ and $1\, ms^{-1}$. Then they collide and stick together. Find the final velocity .............. $\mathrm{m} \mathrm{s}^{-1}$

A body of mass $5\, kg$ moving with a velocity $10\, m/s$ collides with another body of the mass $20\, kg$ at rest and comes to rest. the velocity of the second body due to collision is ............ $\mathrm{m}/ \mathrm{s}$