$A$ ball is projected from a point $O$ as shown in the figure. It will strike the ground after ........ $s$ $\left(g=10 \, m/s^2\right)$.

$A$ plane is flying horizontally at $98 \, m/s$ and releases an object which reaches the ground in $10 \, s$. The angle made by the object with the horizontal while hitting the ground is ......... $^o$.

An aeroplane is moving with a velocity $u$. It drops a packet from a height $h$. The time $t$ taken by the packet in reaching the ground will be

$A$ ball is thrown from a rooftop at an angle of $45^\circ$ above the horizontal. It hits the ground a few seconds later. At what point during its motion does the ball have $(a)$ greatest speed, $(b)$ smallest speed, and $(c)$ greatest acceleration? Explain.

$A$ boy playing on the roof of a $10 \, m$ high building throws a ball with a speed of $10 \, m/s$ at an angle $30^{\circ}$ with the horizontal. How far from the throwing point will the ball be at the height of $10 \, m$ from the ground (in $, m$)? $(g = 10 \, m/s^2, \sin 30^{\circ} = 1/2, \cos 30^{\circ} = \sqrt{3}/2)$

$A$ body is projected from the top of a tower with a velocity $\overrightarrow{u} = 3 \hat{i} + 4 \hat{j} + 5 \hat{k} \text{ m/s}$, where $\hat{i}, \hat{j},$ and $\hat{k}$ are unit vectors along east, north, and vertically upwards, respectively. If the height of the tower is $30 \text{ m}$, find the horizontal range of the body on the ground. (Take $g = 10 \text{ m/s}^2$) (in $\text{ m}$)