Two bodies are projected with the same velocity. If one is projected at an angle of ${30^o}$ and the other at an angle of ${60^o}$ to the horizontal, the ratio of the maximum heights reached is

A boy playing on the roof of a $10\, m$ high building throws a ball with a speed of $10\,m/s$ at an angle of $30^o$ with the horizontal. How far from the throwing point will the ball be at the height of $10\, m$ from the ground ?  $\left[ {g = 10\,m/{s^2},\sin \,{{30}^o} = \frac{1}{2},\cos \,{{30}^o} = \frac{{\sqrt 3 }}{2}} \right]$

A particle is projected from the ground at an angle of $\theta $ with the horizontal with an initial speed of $u$. Time after which velocity vector of the projectile is perpendicular to the initial velocity is

A projectile is thrown from a point in a horizontal plane such that the horizontal and vertical velocities are $9.8 \;ms ^{-1}$ and $19.6\; ms ^{-1}$. It will strike the plane after covering distance of ........ $m$

 The $x-t$ graph of a particle moving along a straight line is shown in figure The $v-t$ graph of the particle is correctly shown by

Two projectiles, one fired from surface of earth with velocity $10 \,m/s$ and other fired  from the surface of another planet with initial speed $5\, m/s$ trace identical trajectories.  The value of acceleration due to the gravity on the planet is   ......... $m/s^2$