$A$ ball is thrown upward from the top of a building at an angle of $30^{\circ}$ to the horizontal and with an initial speed of $20 \,m/s$. If the ball strikes the ground after $3 \,s$, then the height of the building is (acceleration due to gravity $g = 10 \,m/s^2$) (in $\,m$)

From a tower of height $h$,one ball is thrown downwards with a velocity $u$ and another ball is thrown horizontally with the same velocity $u$. What is the ratio of their velocities when they reach the ground?

$A$ block starts from rest at the top of a frictionless slide at a height $h_1$ above the ground. The block leaves the slide moving perfectly horizontally at a height $h_2$ above the ground. The block eventually hits the ground travelling at an angle $\theta = 30^\circ$ below the horizontal. Then:

$A$ child stands on the edge of a cliff $10 \ m$ above the ground and throws a stone horizontally with an initial speed of $5 \ m/s$. Neglecting air resistance,the speed with which the stone hits the ground will be $.......... \ m/s$ (given,$g = 10 \ m/s^2$).

From the top of a tower of height $40\,m$,a ball is projected upwards with a speed of $20\,m/s$ at an angle of elevation of $30^{\circ}$. The ratio of the total time taken by the ball to hit the ground to its time of flight (time taken to come back to the same elevation) is (take $g=10\,m/s^2$).

$A$ gun can fire shells with maximum speed $v_0$ and the maximum horizontal range that can be achieved is $R = \frac{v_0^2}{g}$. If a target farther away by distance $\Delta x$ (beyond $R$) has to be hit with the same gun,show that it could be achieved by raising the gun to a height at least $h = \Delta x \left[ 1 + \frac{\Delta x}{R} \right]$.