Question about air resistance

MrPeanut

So, I have been thinking about this idea for a long time. I have heard that if you travel behind a semi-truck, then you drive within a pocket of stagnant air behind the truck and will end up using less gas because of this... My question is, if I attached a large piece of plywood in front of my car to a long metal bar mounted to my car, with the plywood being perpendicular to the ground and parallel to the front of my car, then would I be able to use less gas on my trip? I really really need to save money on gas.. I have attached a schematic image depicting the situation. Tell me if I will use less gas on my trip.

Drakkith

You will not save any gas. The reason you save gas by being behind a large truck is because the truck itself is doing the work and pushing the air out of the way. The air in the pocket is moving along with the truck and you simply drive up into it. Attaching plywood to the front of your car doesn't do anything as your car is still what has to push the air out of the way. (Or rather your car's engine still has to provide the power to push it out of the way since the wood is attached to your car.)

Lsos

Or rather, it DOES serve to waste even more gas as a piece of plywood attached to the car has terrible aerodynamic properties. You will increase the air resistance to beyond that of the least aerodynamic vehicle I can think of.

BTW, replacing the plywood with a big magnet (to pull your car forward) will also not save any gas :)