OR: What would be the effect on the maximum range in doubling the velocity of a projectile?
Let a body be projected with velocity $u$ by making an angle $\theta$ with horizontal. If $R$ is the horizontal range of the projectile, then \[R=\frac{u^2\sin2\theta}{g}\]
If the velocity of firing is doubled, $u’=2u.$ Then, the new range will be \[R’=\frac{u’^2\sin2\theta}{g}=\frac{4u^2\sin2\theta}{g}=4R\]
So, the new range will be four times the original.
[Read: Projectile Motion]