An object is projected from ground with speed $20 \,m / s$ at angle $30^{\circ}$ with horizontal. Its centripetal acceleration one second after the projection is .......... $m / s ^2$ [Take $g=10 \,m / s ^2$ ]

Choose the correct alternative $(s)$

A player throws a ball that reaches to the another player in $4\,s$. If the height of each player is $1.5\,m$, the maximum height attained by the ball from the ground level is  .......... $m$

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 ......... $^o$

The velocity at the maximum height of a projectile is $\frac{\sqrt{3}}{2}$ times its initial velocity of projection $(u)$. Its range on the horizontal plane is .............

A projectile is fired at an angle of $45^o $ with the horizontal . Elevation angle of the projectile at its highest point as seen from the point of projection, is