A piece of marble is projected from earth's surface with velocity of $19.6 \sqrt{2}\,m / s$ at $45^{\circ}.$ $2\,s$ later its velocity makes an angle $\alpha$ with horizontal, where $\alpha$ is $..........$
$45^{\circ}$
$30^{\circ}$
$60^{\circ}$
$0^{\circ}$
A projectile is thrown with an initial velocity of $(a \hat{ i }+b \hat{ j }) ms ^{-1}$. If the range of the projectile is twice the maximum height reached by it, then
Four bodies $P, Q, R$ and $S$ are projected with equal velocities having angles of projection $15^o , 30^o , 45^o $ and $60^o $ with the horizontal respectively. The body having shortest range is
The position coordinates of a projectile projected from ground on a certain planet (with no atmosphere) are given by $y=\left(4 t-2 t^2\right) m$ and $x =(3 t)$ metre, where $t$ is in second and point of projection is taken as origin. The angle of projection of projectile with vertical is .........
The time of flight of an object projected with speed $20 \,ms ^{-1}$ at an angle $30^{\circ}$ with the horizontal, is .... $s$