You will need to be a little more specific to get a good answer, but from what you wrote, it sounds like an elementary dynamics problem that any good dynamics text should help you with. [sig]<p>Nigel Waterhouse<br><a href=mailto:n_a_waterhouse@hotmail.com>n_a_waterhouse@hotmail.com</a><br><a href= > </a><br>A licensed aircraft mechanic and graduate engineer. Attended university in England and graduated in 1996. Currenty,living in British Columbia,Canada, working as a design engineer responsible for aircraft mods and STC's.[/sig]