The relation between the horizontal displacement $x$ (in metre) and the vertical displacement $y$ (in metre) of a projectile is $y = 3x - 0.8x^2$. The time of flight of the projectile is (Acceleration due to gravity $g = 10 \ m/s^2$). (in $s$)

$A$ boy standing on a moving truck throws a projectile such that he is able to catch it back after the truck has moved $100 \,m$. If the truck is moving horizontally along a straight line with a constant speed $30 \,m/s$, at what speed (relative to the truck) must the projectile be thrown? (Assume $g = 10 \,m/s^2$)

If the range of a gun which fires a shell with muzzle speed $V$ is $R$,then the angle of elevation of the gun is

$A$ particle covers $50\, m$ distance when projected with an initial speed. On the same surface,it will cover a distance of ......... $m$ when projected with double the initial speed.

$A$ stone is projected from the ground with velocity $25\,m/s$. Two seconds later,it just clears a wall $5\,m$ high. The angle of projection of the stone is ........ $^o$ $(g = 10\,m/s^2)$.

At the highest point of the path of a projectile,its