# Water Rocket-density,temp,drag

1. Nov 17, 2007

### thereddevil

I have a question about rockets
This involves the d and temp of the water

m | -
a | -
s | -
s | -
| -
|-_________________
density
So graph should look like ^^
and pV =(proportional to) d
d=m/volume
d=m(mass)
d=mv
density proportional to velocity

Are sure that the greater the density of the water (using salt) the greater the momentum( initial velocity of the rocket) ???
Because thinking practically if you were to put lots of salt in, then it would not work normally. However i do understand where your coming from because the more fuel that is expelled at x speed the greater the velocity so therefore the greater the mass of this fuel at the same x speed the greater the v, right???

Also for temp
pV=nRT ot pV/nR = T
d=m/v
to form V=m/d

therefore
T= (pm/d)/nR
if density is proportional to mv
T is proportional to pm/velocity ?
or T proportional to 1/v
making graph curved like
y axis velocity
|
|
* |
** |
*** -
********* -
***************** - - x axis temperature

Is this right because im really stuck as i didnt have time to finish all experiments.

Also working out the drag of the rocket.
Would i need to work out the Cross Sec Area or the frontal surface eg the whole nose cone plus the wings where you can see them looking down onto it??

thanks for the help!