A ball is thrown upwards and it returns to ground describing a parabolic path. Which of the following remains constant

A missile is fired for maximum range at your town from a place $100\, km$ away from you. If the missile is first detected at its half way point, how much warning time will you have ? (Take $g = 10\, m/s^2$)

A body is projected at such an angle that the horizontal range is three times the greatest height. The angle of projection is

The time of flight of an object projected with speed $20 \,ms ^{-1}$ at an angle $30^{\circ}$ with the horizontal, is .... $s$

A projectile is launched at an angle ' $\alpha$ ' with the horizontal with a velocity $20 \; ms ^{-1}$. After $10 s$, its inclination with horizontal is ' $\beta$ '. The value of $\tan \beta$ will be : $\left( g =10 \; ms ^{-2}\right)$

A ball is projected with a velocity, $10 ms ^{-1}$, at an angle of $60^{\circ}$ with the vertical direction. Its speed at the highest point of its trajectory will be$............... ms ^{-1}$