Match the columns

Column $-I$     $R/H_{max}$	Column $-II$   Angle of projection $\theta $
$A.$ $1$	$1.$ ${60^o}$
$B.$ $4$	$2.$ ${30^o}$
$C.$ $4\sqrt 3$	$3.$ ${45^o}$
$D.$ $\frac {4}{\sqrt 3}$	$4.$ $tan^{-1}\,4\,=\,{76^o}$

 

In the motion of a projectile freely under gravity, its

A particle is projected from horizontal making an angle of $53^{\circ}$ with initial velocity $100\,m / s$. The time taken by the particle to make angle $45^{\circ}$ from horizontal is $.........\,s$

A projectile is thrown with velocity $U=20\ m/s ± 5\%$ at an angle $60^o.$ If the projectile falls back on the ground at the same level then    ......... $m$ of following can not be a possible answer for range.

The horizontal range is four times the maximum height attained by a projectile. The angle of projection is  .......... $^o$

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 $g = 10\, m/s ^2$) the maximum height of the missile is