$A$ ball of mass $1\,kg$ moving with a velocity of $4\,m/s$ collides with a stationary ball of mass $M$. The collision is oblique. After the collision,the first ball moves at a right angle to its initial direction with a velocity of $3\,m/s$. The momentum of the second ball (in $kg\cdot m/s$) after the collision would be nearly:

$A$ set of $n$ identical cubical blocks lies at rest parallel to each other along a line on a smooth horizontal surface. The separation between the near surfaces of any two adjacent blocks is $L$. The block at one end is given a speed $v$ towards the next one at time $t = 0$. All collisions are completely inelastic,then

Fill in the blanks:
$(a)$ If the momentum of an object is doubled,its kinetic energy becomes ........
$(b)$ For a perfectly inelastic collision,the coefficient of restitution $e$ $=$ .....
$(c)$ An appliance with $1\,kW$ power consumes $1\,kWh$ of energy in ....... time.

$A$ spherical bowl of radius $R = 2 \ m$ is placed on a horizontal plane. $A$ particle of mass $m = 1 \ g$ oscillates on its inner surface. If the particle starts from a point on the bowl at a height of $h = 1 \ cm$ from the horizontal plane and the coefficient of friction is $\mu = 0.01$,find the total distance $s$ traveled by the particle before it comes to rest at the bottom of the bowl. (in $m$)

$A$ block of mass $m$ moving with a velocity $v_0$ on a smooth horizontal surface strikes and compresses a spring of stiffness $k$ until the mass comes to rest,as shown in the figure. This phenomenon is observed by two observers:
$A$: standing on the horizontal surface
$B$: standing on the block
According to observer $B$,the potential energy of the spring increases:

$A$ train of mass $3 \times 10^6 \ kg$ is accelerated by an engine such that its velocity increases from $5 \ m/s$ to $25 \ m/s$ in $5 \ minutes$. The power of the engine is ........ $MW$.