## anonymous 3 years ago Can anyone help me out with this problem: A ball is thrown vertically upward with initial velocity v. Find the maximum height H of the ball as a function of v. Then find the initial velocity v required to achieve a height of H.

1. anonymous

we'll just use the eq, $$v^2 = u^2 +2aS$$, since u=0, a=-g,(since it is opposite direction of v), rearranging gives $$S=\frac{v^2}{2g}$$

2. anonymous

where S=H

3. anonymous

ive arrived at this answer too...however when i submitted it...it said that g was not defined in this context

4. anonymous

is there any way to answer this in terms of H and v only?

5. anonymous

or, you can just sub g=10 into it

6. anonymous

thats what i would think so too. but it still says that answer is incorrect

7. anonymous

oh oh. sorry. my mistake. it's initial velocity, not end velocity. since v=0, $$u=\sqrt{2gH}=\sqrt{19.8H}$$

8. anonymous

tried that one too unfortunately....im not sure what they looking for

9. anonymous

dang==then i have no idea what they want

10. anonymous

thanks for trying to help though. ...its very much appreciated :)

11. anonymous

you're welcome :)