A heavy particle is projected from a point on the horizontal at an angle $60^o$ with the horizontal with a speed of $10\ m/s$ . Then the radius of the curvature of its path at the instant of crossing the same horizontal will be    ......... $m$

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

The range of a projectile for a given initial velocity is maximum when the angle of projection is ${45^o}$. The range will be minimum, if the angle of projection is ......... $^o$

Aball is thrown from a point on ground at some angle of projection. At the same time a bird starts from a point directly above this point of projection at a height $h$ horizontally with speed $u$. Given that in its flight ball just touches the bird at one point. Find the distance on ground where ball strikes

Ratio between maximum range and square of time of flight in projectile motion is

If the initial velocity of a projectile be doubled, keeping the angle of projection same, the maximum height reached by it will