Projectile motion flight time of ball

[ronny45]

[SOLVED] Projectile motion

Homework Statement

A ball is thrown with an intial velocity of v0 at an angle theta from the horizontal. Find the flight time of the ball in terms of H and g only.

Homework Equations

t = (2 v0 sin theta)/g

The Attempt at a Solution

Ok. I found theta to be the tan inverse of 4R/H. Thus, the initial velocity is sqrt[Rg/sin(2tan-1(4R/H))] - a little longwinded but accurate. However, my problem arises when I plug these values into the above equation and those really nasty 'R's refuse to go away, and the problem specifically states that g and H should be my only variables. I feel like i must be missing something really obvious, and if so, i apologise in advance, but please help anyway! Thank you!

 

[rl.bhat]

When the ball reaches the height H, its velocity is equal to zero. So using kinametics equation we get (vosin theta)^2 = 2gH. From this equation find the value of (v0sin theta) and plug it the relevant equation.