MadSci Network: Physics

Re: Jet boat thrust measurement. Above or below water surface

Date: Wed Sep 3 17:19:56 2003
Posted By: Dennis K. Van Gemert, Systems Engineer
Area of science: Physics
ID: 1062105267.Ph

Drawing from the basics of rocket propulsion, we know that the thrust is equal to the product of the mass flow rate and nozzle exit velocity plus the product of the nozzle exit area and the difference between the nozzle exit pressure and the ambient pressure.

The product of the nozzle exit area and the ambient pressure is referred to as the back-pressure.  Since the density of water is greater than that of air, it follows that the back-pressure in water is greater than in air; and thus, the thrust is less.

Current Queue | Current Queue for Physics | Physics archives

Try the links in the MadSci Library for more information on Physics.

MadSci Home | Information | Search | Random Knowledge Generator | MadSci Archives | Mad Library | MAD Labs | MAD FAQs | Ask a ? | Join Us! | Help Support MadSci

MadSci Network,
© 1995-2003. All rights reserved.