A projectile is thrown with some initial velocity at an angle $\alpha$ to the horizontal. Its velocity when it is at the highest point is $(2 / 5)^{1 / 2}$ times the velocity when it is at height half of the maximum height. Find the angle of projection $\alpha$ with the horizontal.

A bullet is fired from a gun at the speed of $280\,ms ^{-1}$ in the direction $30^{\circ}$ above the horizontal. The maximum height attained by the bullet is $........\,m$ $\left(g=9.8\,ms ^{-2}, \sin 30^{\circ}=0.5\right):-$

The equation of motion of a projectile is $y=12 x-\frac{3}{4} x^2$ $..........\,m$ is the range of the projectile.

A ball is projected from ground with a speed of $20\,m / s$ at an angle of $45^{\circ}$ with horizontal. There is a wall of $25\,m$ height at a distance of $10\,m$ from the projection point. The ball will hit the wall at a height of $.........\,m$

For a projectile, the ratio of maximum height reached to the square of flight time is ($g = 10 ms^{-2}$)

A stone is projected from ground at $t = 0$. At the time of projection horizontal and vertical component of velocity are $10\, m/s$ and $20\, m/s$ respectively. Then time at which tangential and normal acceleration magnitude will be equal $(g = 10\, m/s^2)$ [neglect air friction]    ......... $\sec$