I own a hovercraft. She does about 40 M.P.H. on water and land. Ice is a different story. The hovercraft pumps out about 100 M.P.H. wind for push. My question is, if a truck is driving behind the hovercraft about 5 feet with a big sheet of plywood strapped to the front of the truck, so the wind is hitting it. Would the crafts speed increase?
I don't think so. If there is no contact between the craft and the wood then the same physical laws apply...action/reaction. It's the movement of the air creating the thrust, it doesn't matter if it's acting on more air or a piece of wood...I guess. Then again I could be wrong :)
Theoretically yes, but in reality the wind resistance at those sort of speeds probably doesn't account for much. Road resistance is your main thing. You may see an improvement of 1mph or something, but that'll probably be it.
The pressure gradient behind a fan dissipates rapidly outward. (unless directed as within a tube). This is why the crafts shroud hovers only a slight distance above the surface.
My gut feeling is yes because the truck will essencially push the hovercraft and the jet of air wich is expelled back wards, however given the last ans this might not be the case, I guess it will dep on the forces involved.