# Water Rocket

1. Nov 2, 2008

### wsbkp08

1. The problem statement, all variables and given/known data
Hi, guys.
I did a project but questions are killing me right now.
I was going all the tutorials but I really have no idea.
What we did was water rocket project.
Here are the data
Ttotal - avg. 9.96 sec.
Avg. Apogee - 2.94 sec.

2. Relevant equations

3. The attempt at a solution

I need to find the v initial, ymax, and the maximum range.
Here is how I did it

For Vinitial
DeltaY(0) =(Vinitial)(5.88)+(1/2)(-9.8)(5.88)^2
Vinital = 28.8m/s
5.88sec comes from avg. apogeeX2 ------> (2.94)(2)

For Ymax,
Ymax= (Vinital)(time)+(1/2)(-9.8)(time)
(28.8)(2.94)+(1/2)(-9.8)(2.94)^2
= 42.3 m

For maximum Range,
I found out that cos 45 will give me maximum range so

Range=(Vinital)(cos45)(time)
(28.8)(cos45)(5.88)
= 119.7 m

Lastly, my teacher asked, "What role does the water play in making the rocket move?"
He also asked for relevent formulas and a diagram illustrating the forces.
Only thing we learned so far are Horizontal Projectil motion and free fall.
I do not think we ever learned this.
Thanks guys.

Last edited: Nov 2, 2008
2. Nov 2, 2008

### wsbkp08

Oh, I realized I had to put what I did.
here is what I did..
for Vinitial,
I did
deltaY=(Vinitial)(5.58)+(1/2)(-9.8)(5.88)^2
and got Vinitial=28.8m/s.
5.88 comes from avg. apogee= 2.94X2=5.58

For Ymax,
I did
Ymax = (28.8)(2.94)+(1/2)(-9.8)(2.94)^2
Ymax = 42.3 m

Lastly, for Range
Since Range max, I found that cos 45 will give me maximum range
So,
Range=(Vinital)(cos45)(time)
(28.8)(cos45)(5.88)
Range=119.7m.

Here is how i did it.
But honestly,
on the last problem with "what role does the water play in making the rocket move?"
I abs. have no idea.
Thanx guys.