If the range of a projectile is twice its maximum height,what is the range?

$A$ shell is fired vertically upwards with a velocity $v_1$ from a trolley moving horizontally with velocity $v_2$. $A$ person on the ground observes the motion of the shell as a parabola,whose horizontal range is ....

The horizontal range of a projectile is $4\sqrt{3}$ times its maximum height. Its angle of projection will be ......... $^\circ$.

Average velocity of a particle in projectile motion between its starting point and the highest point of its trajectory is: (projection speed = $u$,angle of projection from horizontal = $\theta$)

The trajectory of a projectile,projected from the ground,is given by $y = x - \frac{x^2}{20}$,where $x$ and $y$ are measured in meters. The maximum height attained by the projectile will be $...........\,m$.

$A$ ball is thrown at different angles with the same speed $u$ and from the same point. It has the same range in both cases. If $y_1$ and $y_2$ are the heights attained in the two cases,then $y_1 + y_2$ is equal to: