In the graph shown in the figure, which quantity associated with projectile motion is plotted along the $y$-axis?

$A$ body is projected with a speed $u \ m/s$ at an angle $\beta$ with the horizontal. The kinetic energy at the highest point is $3/4$ of the initial kinetic energy. The value of $\beta$ is: (in $^{\circ}$)

The range of a projectile for a given initial velocity is maximum when the angle of projection is $45^\circ$. The range will be minimum,if the angle of projection is ......... $^\circ$.

The velocity of projection of a body is increased by $2 \%$. Other factors remaining unchanged,what will be the percentage change in the maximum height attained? (in $\%$)

At the highest point of the path of a projectile,its

$A$ projectile is projected in such a way that it achieves maximum range for a given velocity. Find the velocity of the projectile at its maximum height.