# Homework Help: Projectile with fixed angle and tripled velocity

1. Jan 27, 2009

### enantiomer1

1. The problem statement, all variables and given/known data
Hi, I'm stuck on this problem (it seems simple but I can't seem to get it down),
The question is, "A certain cannon with a fixed angle of projection has a range of 1500 m. What will be its range if you add more powder so that the initial speed of the cannonball is tripled?"

2. Relevant equations
d=vhori*t
d=vhori cos theta * t

3. The attempt at a solution
At first I simply saw this as a distance versus velocity and time problem (x=v0x*t so I simply tripled the distance getting 4500; not surprisingly, I was wrong. I'm sure that the equation relies on the 'fixed angle' part of the equation so I simply divided the equation by 21/2 (due to cos theta) getting 3192, but I'm still wrong, what variable am I forgetting?

2. Jan 27, 2009

### LowlyPion

Welcome to PF.

If you triple the speed, what do you do to the horizontal velocity?

What does tripling the speed do to the time to max height and back down?

Distance is v * t so ...