# Homework Help: Initial velocity of projectile given angle and max height

1. Aug 26, 2012

### ulfy01

1. The problem statement, all variables and given/known data
A projectile was fired across level ground at an initial angle of 43.00 degrees above the horizontal. During its flight, it reached a maximum height of 2974 metres. What was the initial speed of this projectile?

2. Relevant equations

I assume that the correct equation to use is Vy2 = V0y² - 2g(y - y0).

3. The attempt at a solution

To be honest I'm not even sure how to go about it. Given the equation, I would rearrange for V0y² however that doesn't seem to work at all. I'm not even sure what the value of Vy has to be. I also suspect the angle comes into play, but I'm not sure what it can tell me. Any pointers greatly appreciated.

2. Aug 26, 2012

### CAF123

At the top of the flight, there is no vertical component of velocity, so $v_y = 0$ there. You are also correct that the angle is involved. Indeed, $v_o\sinθ= v_{oy}$ and it is this $v_o$ that you are solving for.