I need some help

[Becker4]

i would see what the rules state

if the tank does not have to be carried by the car get a ping pong ball and a verry large drum of water and pour it down the track

of course, this scheme has the added bonus of washing away the opponents car. two for one!

[Ciro Pabón]

Becker is right: a rocket that "burns" all the fuel at once (if achievable) is better than one that burns it slowly. For example, Apollo 8 (the first craft to do such a manouver) burnt all his fuel on the moon's orbit, when coming back to Earth. This way you do not have to "carry back" to Earth some of the fuel (while it burns), only the capsule.

In the science-fiction book "Rendezvous with Rama", by Arthur Clark, the raman spaceship does the same thing: its manouver to change course takes place a few kilometers over the sun's surface. Clark's argument is the same as Becker: this way they do not have to carry the fuel spent "in the bottom of the gravity well of the sun", and the fuel weight is acting all the way while they fall unto the sun: this is the most efficient way for a rocket.

[Crabbia]

Thanks for the help with the picure posting thing Mr Pabón, 'preciate it.

And again i agree with bekker and ciro that using the water in a short burst would be most effective but the 'drivetrain' of the car must then be super slick. I'm just worried that if it isnt the water might all be spent before the end of the race and the car would slow down due to the friction converting the kinetic energy. Remember if all the fuel is spent the car has less mass and therfore carries less momentum. You're trading momentum for speed if u like. This is very effective for spaceships as described by ciro precisely because in space there is no friction and u need all the speed you can get in a short burst to break the pull of gravity.

But to this end i suggest a pipe as long as is practically possible. this would give you maximum thrust when the vehicle is at it most heavy supply the initial force to surmount the inertia of the vehicle plus water system. thereafter the system will loose mass but gain speed as the mass from the water eave the system but due to the properties of inertia the car will get faster.

I'm getting way too far into mechanics in my spare time for my liking.

A Suggestion Rafeal, once u have decided on a final design, make little adaptors out of rubber or pvc O-rings of different diameters that u can attach to the water jet exit. this way you can physically test what diameter, and hence flow rate would work the best. another thing u can try is the case where there may be too much water in the tank. This might be possible as the benifits of the added pressure by an increase in water in the tank might outweighed by the deficit of having to much 'fuel' on board.

From practical experience, like pressure hoses, the smaller the hole the more force acting. but this force is also a function of the pressure acting so u'll have to test at different pressure levels.