A point mass $M$ moving with a certain velocity collides with a stationary point mass $M / 2$. The collision is elastic and in one-dimension. Let the ratio of the final velocities of $M$ and $M / 2$ be $x$. The value of $x$ is
$2$
$3$
$1/2$
$1 / 4$
Two identical balls $A$ and $B$ are released from the positions shown in figure. They collide elastically on horizontal portion $MN$ . The ratio of the heights attained by $A$ and $B$ after collision will be : (neglect friction)
A large block of wood of mass $M =5.99\, kg$ is hanging from two long massless cords. A bullet of mass $m =10\, g$ is fired into the block and gets embedded in it. The (block $+$ bullet) then swing upwards, their centre of mass rising a vertical distance $h =9.8\,cm$ before the (block $+$ bullet) pendulum comes momentarily to rest at the end of its arc. The speed of the bullet just before collision is: (Take $g =9.8\, ms ^{-2}$ ) (in $m/s$)
$Assertion$ : $n$ small balls each of mass $m$ colliding elastically each second on surface with velocity $u$. The force experienced by the surface is $2\,mnu$.
$Reason$ : On elastic collision, the ball rebounds with the same velocity.
Two particles of masses ${m_1}$ and ${m_2}$ in projectile motion have velocities ${\vec v_1}$ and ${\vec v_2}$ respectively at time $t = 0$. They collide at time ${t_0}$. Their velocities become ${\vec v_1}'$ and ${\vec v_2}'$ at time $2{t_0}$ while still moving in air. The value of $|({m_1}\overrightarrow {{v_1}} '\, + {m_2}\overrightarrow {{v_2}} ') - ({m_1}\overrightarrow {{v_1}} \, + {m_2}\overrightarrow {{v_2}} )$| is
Two persons $A$ & $B$ are throwing ball of $200\ g$ on wall as shown in figure. Balls strike wall perpendicularly at same point height $2\ m$ from ground. Ball strike wall elastically at same time and returns back to $A$ & $B$, at same time. They again repeat the same. What is the average force on wall ..................... $\mathrm{N}$ (take $g = 10\ m/s^2$)