# Homework Help: Projection Angle?

1. Oct 17, 2007

### chitownfireman

My teacher gave me this problem today and I have tried everything I know but I still haven't found the right answer. If anyone knows how to solve it, please share. Thanks

At what projection angle will the range of a projectile equal its maximum height?

Hint: 2 sin θ cos θ = sin 2 θ

2. Oct 17, 2007

### cristo

Staff Emeritus
Presumably you've either been given a formula for the range of a projectile, or know the kinematic equations and can derive such an equation. Do the usual thing, split up into vertical and horizontal components, and solve for each separately.

You need to show some work before you get any real help, and should note that solutions are not provided on these forums at all. In future, also, please post in the homework forums. Oh, and welcome to PF.

3. Oct 17, 2007

### chitownfireman

4. Oct 17, 2007

### saiaspire

the angle is 76

5. Oct 17, 2007

### chitownfireman

Thanks mate, but I never wanted the exact answer, I just wanted a push in the right direction. You may be right, but I am currently trying to figure it out, but thanks for the input.

6. Oct 17, 2007

### saiaspire

Let A be the angle and u be the velocity of projection and g ( accel due to gravity)
Range (R) = u^2sin A^2/2g

Max Height(H)=u^2sin2 A/g

sin 2 A = 2 sin A cos A

equate R and H ( since they should be equal)..

u will get sin A/cos A = 4

but sin A/cos A = tan A

therfore A should be 76 degrees...

7. Oct 17, 2007

### rocomath

you're not suppose to give out full solutions or the answer.