# Homework Help: Interesting angle of elevation problem

1. Oct 18, 2012

### steven1495

1. The problem statement, all variables and given/known data
What is the angle of elevation of a projectile that travels THREE time horizontally its MAXIMUM height, on earth

g = 9.800m/s2

2. Relevant equations

Equation 1 - H = ((vsinθ)2)/2g

Equation 2 - R = 2v2((sinθcosθ)2/g

3. The attempt at a solution

I tried making 3x(equation 1)=equation 2, and letting v=5m/s, and then solving for θ, but I don't think I rearranged the equation properly. THE ANSWER IS FOR SURE 53.13°, I JUST HAVE TO SHOW HOW TO GET IT
Thanks for any help

Last edited: Oct 18, 2012
2. Oct 18, 2012

### lewando

Equation for range is not right.

3. Oct 18, 2012

### steven1495

What is the equation for range? And could you help me with it?

4. Oct 18, 2012

### lewando

R = 2v2sinθcosθ/g. That should get you going.

5. Oct 18, 2012

### steven1495

i still can't figure it out

6. Oct 18, 2012

### lewando

Nothing wrong with your original approach (3H = R). Show your work so you can more specifically show where you are having a problem.

7. Oct 18, 2012

### steven1495

I dont need help with that one anymore, but if you could help me with a different problem, it would be great.

a)To what elevation must one go to decrease your "weight" to one sixteenth (1/16) of its "surface" value?

b) At the elevation calculated in part a), what is the period of this orbit?

G = 6.670x10^-11
R(earth) = 6.380x10^6
M(earth) = 5.98x10^24

8. Oct 18, 2012

### lewando

You should start a new thread, following the template, listing all relevant equations, showing your work, etc.

9. Oct 18, 2012

### steven1495

thats all i have, i have no idea how to solve it