# Projectile Motion comparing height and initial velocity

Hey,
I came across this question in my text book, and there isnt an answer for it in the back, so I would just like to check if I have my head around it.

The question is:
2 projectiles are launched at the same angle. Projectile 1 reaches a max height of twice that of the projectile 2. What is the ration of the initial speeds?

I said that they where in the ratio 4:1, as one of the formulas is: y=yo +voyt -0.5gt^2
and because the height is doubled, the time taken must also be doubled?
am I correct in saying this?

Thanks

## Answers and Replies

Doc Al
Mentor
I said that they where in the ratio 4:1, as one of the formulas is: y=yo +voyt -0.5gt^2
and because the height is doubled, the time taken must also be doubled?
am I correct in saying this?
No.

Come up with a formula that relates max height with initial velocity without the need for the time.

I got an answer or root(2), is this correct?

Doc Al
Mentor
I got an answer or root(2), is this correct?
Yes.

Thank you very much!