$A$ particle is dropped from the top of a tower. The distance covered by it in the last one second is equal to the distance covered by it in the first three seconds. The height of the tower is $....m$

From the top of a tower,a particle is thrown vertically downwards with a velocity of $10\; m/s$. The ratio of the distances covered by it in the $3^{rd}$ and $2^{nd}$ seconds of the motion is (Take $g = 10\; m/s^2$).

An object of mass $5 \, kg$ is thrown vertically upwards from the ground. The air resistance produces a constant retarding force of $10 \, N$ throughout the motion. The ratio of time of ascent to the time of descent will be equal to [Use $g = 10 \, ms^{-2}$]

$P, Q$ and $R$ are three balloons ascending with velocities $U, 4U$ and $8U$ respectively. If stones of the same mass are dropped from each when they are at the same height $h$,which stone reaches the ground first?

$A$ parachutist after bailing out falls $50\, m$ without friction. When the parachute opens,it decelerates at $2\, m/s^2$. He reaches the ground with a speed of $3\, m/s$. At what height did he bail out (in $, m$)?

$A$ boy standing at the top of a tower of $20 \, m$ height drops a stone. Assuming $g = 10 \, m/s^2$,the velocity with which it hits the ground is ......... $m/s$.