$A$ stone is projected at an angle of $60^o$ from the ground level and strikes at an angle of $30^o$ on the roof of a building of height $h = 30 \, m$. Find the speed of projection (in $m/s$) of the stone.

Three balls,$A, B$ and $C$ are released and all reach the point $X$ (shown in the figure). Balls $A$ and $B$ are released from two identical structures,one kept on the ground and the other at height $h$ from the ground as shown in the figure. They take time $t_A$ and $t_B$ respectively to reach $X$ (time starts after they leave the end of the horizontal portion of the structure). The ball $C$ is released from a point at height $h$,vertically above $X$ and reaches $X$ in time $t_C$. Choose the correct option.

$A$ helicopter flying horizontally with a speed of $360 \ km/h$ at an altitude of $2 \ km$,drops an object at an instant. The object hits the ground at a point $O$,$20 \ s$ after it is dropped. The displacement of $O$ from the position of the helicopter where the object was released is: (use acceleration due to gravity $g = 10 \ m/s^2$ and neglect air resistance)

An airplane is flying at a height of $490 \, m$ with a horizontal velocity of $60 \, km/h$. When the airplane is exactly above point $A$,a package is dropped from it. At what distance from point $A$ will the package hit the ground (in $/3 \, m$)? $(g = 9.8 \, m/s^2)$

$A$ player throws a ball that reaches another player in $4\,s$. If the height of each player is $1.5\,m$,the maximum height attained by the ball from the ground level is .......... $m$.

$A$ hiker stands on the edge of a cliff $490 \; m$ above the ground and throws a stone horizontally with an initial speed of $15 \; m/s$. Neglecting air resistance,find the time taken by the stone to reach the ground,and the speed with which it hits the ground. (Take $g = 9.8 \; m/s^2$).