Which of the following statements is true?

$A$ bullet loses $\left( \frac{1}{n} \right)^{th}$ of its velocity while passing through one plank. The number of such planks required to stop the bullet is:

Two trolleys of mass $m$ and $3m$ are connected by a spring. They are compressed and released; once released,they move off in opposite directions and come to rest after covering distances $S_1$ and $S_2$ respectively. Assuming the coefficient of friction to be uniform,the ratio of distances $S_1:S_2$ is:

Two solid rubber balls $A$ and $B$ have masses $200 \ g$ and $400 \ g$ respectively. They are moving towards each other,with ball $A$ having a velocity of $0.3 \ m/s$. After the collision,both balls come to rest. What is the velocity of ball $B$ in $m/s$?

$A$ particle of mass $m$ moving horizontally with velocity $v_0$ strikes a smooth wedge of mass $M$,as shown in the figure. After the collision,the particle starts moving up the inclined face of the wedge and rises to a height $h$. The maximum height $h$ attained by the particle is:

$A$ ball is projected vertically upwards. Air resistance and variation in $g$ may be neglected. The ball rises to its maximum height $H$ in a time $T$,the height being $h$ after a time $t$.
[$1$] The graph of kinetic energy $E_k$ of the ball against height $h$ is shown in figure $1$.
[$2$] The graph of height $h$ against time $t$ is shown in figure $2$.
[$3$] The graph of gravitational potential energy $E_g$ of the ball against height $h$ is shown in figure $3$.
Which of the following shows the correct answers?