wireman Posted June 11, 2012 Report Share Posted June 11, 2012 I'm kinda new to the whole Physics Lab Reports section. I was wondering if this would be a good question to address for my first lab report.How can the the pressure of air and varying quantities of water affect the movement of a model water-powered car of a fixed mass along a horizontal track?Please help me out on this one. Reply Link to post Share on other sites More sharing options...
HiggsHunter Posted June 11, 2012 Report Share Posted June 11, 2012 In view of the hoaxes about "water-powered cars" I would suggest avoiding that term and specifying what technology (electrolysis + fuel cell, etc) your model uses. I would also suggest clarifying what you mean by the pressure of the air in this context. Are you referring to the effect of air pressure on the energy conversion processes, or to the aerodynamic drag on the moving model? 1 Reply Link to post Share on other sites More sharing options...
wireman Posted June 11, 2012 Author Report Share Posted June 11, 2012 I'm planning on using compressed air with water as a fuel. So i don't really know the term for this. By pressure of air, I actually mean the amount of air(volume) being pumped into the container with the water. So I think the more the air, the more the pressure. In that way. Sorry I should have framed my question more precisely.Im just basically analysing the relation between the volume of air pumped, with the water, and the distance travelled with the water. 1 Reply Link to post Share on other sites More sharing options...
HiggsHunter Posted June 11, 2012 Report Share Posted June 11, 2012 Compressed air engines are not unusual, but what is the role of the water in your model? 1 Reply Link to post Share on other sites More sharing options...
wireman Posted June 11, 2012 Author Report Share Posted June 11, 2012 just skip to 2:58 Something like this. I'll be measuring the distance travelled by the mass with varying quantities of water. Obviously the air required would be different for different quantities of water. 1 Reply Link to post Share on other sites More sharing options...
HiggsHunter Posted June 11, 2012 Report Share Posted June 11, 2012 I understand that you will be experimenting with what is usually called a "water rocket car". Be sure to take adequate safety measures! 1 Reply Link to post Share on other sites More sharing options...
wireman Posted June 11, 2012 Author Report Share Posted June 11, 2012 Yeah, that's precisely it. Thank you for being so patient with me. Reply Link to post Share on other sites More sharing options...
HiggsHunter Posted June 11, 2012 Report Share Posted June 11, 2012 Sorry I was so slow to understand what kind of car model you were using!I think that it could be quite tricky to devise a water rocket car that runs in stable fashion on a track, and to build a trigger that can release the rocket consistently at a well-defined air pressure.So the project risks to prove more time-consuming than a lab experiment really merits. But if you are interested in developing the car model outside the context of the school study, you could have some fun with it and make some interesting measurements too.Good luck! Reply Link to post Share on other sites More sharing options...
wireman Posted June 11, 2012 Author Report Share Posted June 11, 2012 I'll give it a shot. If it proves to be too time consuming, I'll just do the rocket thing and base my conclusion on the height reached by the rocket. Thanks a lot . Need the luck. Reply Link to post Share on other sites More sharing options...
wireman Posted June 20, 2012 Author Report Share Posted June 20, 2012 Okay so I finally moved to the water rocket.I kept the angle of the launch constant. And changed the water levels and got varying horizontal distances. The results were that the distance first increased with increasing quantities of water, and then decreased after a point.Now my question is:The water rocket focusses on Newton's 3rd law. To explain the initial positive correlation followed by the negative correlation, is it enough if i just say that in the initial stages the water(reaction mass) is less which causes an equal and opposite force that's less. And if the water's too much, the reaction mass is too much which makes the bottle heavy and the force is not enough move the bottle. How do i explain this mathematically? I thought of the instantaneous force expelled through the bottle equalling the force with which the bottle flies. This instantaneous force is 2 x Pressure on the nozzle x Surface Area of nozzle. However, I'm having trouble calculating this pressure and then correlating this to my graph.Finally, How do i explain this graph mathematically? Reply Link to post Share on other sites More sharing options...
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