Two perfectly elastic balls of same mass m are moving with velocities $u_{1 }\mathrm{and} u_2.$ They collide head on elastically $n$ times. The kinetic energy of the system finally is:

Two smooth spheres made of identical material have masses $m$ and $2m$ undergoes an oblique impact as shown in the figure. The initial velocities of the masses are also shown. The impact force is along the line joining their centres along the $x$-axis. The coefficient of restitution is $\frac{5}{9}$. The velocities of the masses after the impact and the approximate percentage loss in kinetic energy.

$AB$ is an $L$-shaped obstacle fixed on a horizontal smooth table. $A$ ball strikes it at $A$ gets deflected and restrikes it at $B$. If the velocity vector before collision is $\overrightarrow{v}$ and coefficient of restitution of each collision is $e$, then the velocity of ball after its second collision at $B$ is

A $2 \mathrm{kg}$ toy car can move along an $x$ axis. Graph shows force $F_x$, acting on the car which begins at rest at time $t=0$. The velocity of the car at $t=10 \mathrm{s}$ is