# Help with some Projectile problems

1. Oct 5, 2007

### DanielP

Hello fellow forum trolls,

I am currently pondering about this physics problem that was assigned to me on a day I was not in school and I have some confusion on the process in which to solve it.

Essentially we have to cannon out a metal ball through a hoop a certain distance away.

We know the initial velocity of the ball, The DeltaY of the hoop, and we have control over the DeltaX. To pass the project we must determine where to set the Hoop in respect to the launcher to get the ball through.

so far my data goes as follows

The launcher is at 30 degrees launching out at a velocity of 5.85

.............X.................Y
Vi..........5.073 m/s....2.92 m/s
Vf..........5.073 m/s
D...........................| .265m
a...........0...............-9.8 m/s^2
t

So my questions are,

For my final velocity of Y i got 3.711 but I feel that it doesnt seem write. I used the formula Vf^2=Vi^2+2a(DeltaY)
other formulas to use
Vf=Vi+at
Delta=Vi*t+1/2at^2
Delta=((Vi+Vf)/2)*t

After that I cannot figure out how to find DeltaX

If you could point me in the write direction or help check my work that would be amazing.

2. Oct 5, 2007

### nrqed

You must use $a_y = -9.80 m/s^2$. Looks lik eyou used a positive acceleration.
use the equations along y find the time it takes to reach the hoop. Then go along x (where a_x=0) to find the delta x.

3. Oct 5, 2007

### DanielP

Thanks for the help,

New Vfy is -2.274
Time i got .53 s
and for DeltaX I found 2.688 m

thanks for the help

4. Oct 5, 2007

### nrqed

mmmm...

I get -1.83 m/s for $v_{fy}$