Calculating the Angle of a Projectile Fired for 3x Range Horizontally

[jesuslovesu]

A projectile is fired so that its horizontal range is 3 times its max height. What is the angle?

Well, I'm stumped because I thought if I just drew up a triangle and did
arctan(1/3), I would get the correct angle... apparently not.

 

[arildno]

What are the equations of motion?

 

[jesuslovesu]

hmm

x = vx*t
y = -1/2g*t^2

I'm not really sure where to go, how the 1:3 would factor into anything.

 

[arildno]

hmm

x = vx*t
y = -1/2g*t^2

I'm not really sure where to go, how the 1:3 would factor into anything.

Your equation for y is incorrect.

Set up Newton's second law of motion for the system, both directions!