The speed of a projectile at its highest point is $v_1$ and at that point, half the maximum height is $v_2$. If  $\frac{v_1}{v_2}=\sqrt{\frac{2}{5}}$, then find the angle of projection.

Shots are fired simultaneously from the top and bottom of a vertical cliff with the elevation $\alpha =30°, \beta =60°$, respectively (figure). The shots strike an object simultaneously at the same point. If $a=30\sqrt{3} \mathrm{m}$ is the horizontal distance of the object from the cliff, then the height $h$ of the cliff is

figure shows that particle $A$ is projected from point $P$. with velocity $u$ along the plane and simultaneously another particle $B$ with velocity $v$ at an angle $\alpha$ with vertical. The particles collide at point $Q$ on the plane. Then

Two balls are projected from points $A$ and $B$ in vertical plane as shown in figure. $AB$ is a straight vertical line. The balls can collide in mid-air if $\frac{v_1}{v_2}$ is equal to,

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Two particles $P$ and $Q$ are projected simultaneously away from each other from a point $A$ as shown in the figure.

The velocity of $P$ relative to $Q$ in $\mathrm{m} {\mathrm{s}}^{-1}$ at the instant when the motion of $P$ is horizontal is

Two guns on a battleship simultaneously fire two shells at the same speed at enemy ships. If the shells follow the parabolic trajectories shown in the figure, which ship will get hit first?