$A$ body falling from a vertical height of $10 \, m$ pierces through a distance of $1 \, m$ in sand. It faces an average retardation in sand equal to (where $g$ = acceleration due to gravity).

$A$ body is projected upwards with a speed $u$ and the time taken by it to reach the maximum height $H$ is $T$. Pick out the correct statement.

$A$ stone is allowed to fall from the top of a tower $100 \ m$ high and at the same time another stone is projected vertically upwards from the ground with a velocity of $25 \ m/s$. The two stones will meet after ......... $s$.

Water drops fall from a tap onto the floor,$5 \ m$ below,at regular intervals of time. The first drop strikes the floor when the sixth drop begins to fall. The height at which the fourth drop will be from the ground at the instant when the first drop strikes the ground is . . . . . . $m$. $(g = 10 \ m/s^2)$

$A$ man throws a ball vertically upward and it rises through $20 \; m$ and returns to his hands. What was the initial velocity $(u)$ of the ball and for how much time $(T)$ it remained in the air? $[g = 10 \; m/s^2]$

$A$ ball of mass $0.2 \, kg$ is thrown vertically upwards with a velocity of $2 \, m/s$. At the highest point of its trajectory:
$(i)$ What will be the magnitude of its velocity?
$(ii)$ What will be the magnitude of its acceleration?
$(iii)$ What will be the magnitude of the force acting on it? (Take $g = 10 \, m/s^2$.)