$A$ ball projected from the ground vertically upward is at the same height at times $t_1$ and $t_2$. The speed of projection of the ball is [Neglect the effect of air resistance].

From $18 \text{ m}$ height above the ground,a ball is dropped from rest. The height above the ground at which the magnitude of velocity equals the magnitude of acceleration (in the same set of units) due to gravity is . . . . . . $\text{m}$. (Take $g = 10 \text{ m/s}^2$ and neglect the air resistance)

$A$ 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 $, m$)?

$A$ person sitting on the ground floor of a building notices through a window of height $1.5 \; m$ that a ball dropped from the roof of the building crosses the window in $0.1 \; s$. What is the velocity (in $m/s$) of the ball when it is at the topmost point of the window? (Take $g = 10 \; m/s^2$)

Two stones of masses $m_1$ and $m_2$ (such that $m_1 > m_2$) are dropped $\Delta t$ time apart from the same height towards the ground. At a later time $t$,the difference in their speed is $\Delta v$ and their mutual separation is $\Delta s$. While both stones are in flight:

The distance covered by a stone dropped from the top of a building in the last second of its motion is $0.36$ times the total distance travelled by it. The height of the building is (acceleration due to gravity $g = 9.8 \ m/s^2$). (in $m$)