Answer:
[tex]\sqrt{2}V[/tex]
Explanation:
Velocity at maximum height is 0 m/s. With initial velocity, V, height h and acceleration of gravity, g,
[tex]v_f^2 = v_i^2+2as[/tex]
[tex]0^2 = V^2 -2gh[/tex]
g is negative because the motion is against gravity.
[tex]V = \sqrt{2gh}[/tex]
If the maximum height were doubled, then we have
[tex]V_1=\sqrt{2g\times2h} = \sqrt{2}\sqrt{2gh} = \sqrt{2}V[/tex]