Don’t try this at home!
Suppose that it’s a very windy day. The wind is blowing at a relatively constant 30 mph, straight out of the north. I get in my car and find a north/south road and proceed to travel south at 30 mph. I then decide to stick my arm out the window. Will it feel calm or windy? It seems like it should feel calm but I’m not sure.
ETA: Oops, I see this is GQ. Nevertheless, this is my WAG below:
It will probably feel blustery. After all, when you stick your arm out of the window it does not seem like a completely straight wind but rather buffets of wind that move in and out (at least when I do it.) So it will probably feel calm occasionally but then when a pocket of air hits the slipstream the wrong way you will feel a gust hit your arm.
Agreed…the car causes turbulence in the air as it passes through it. Even if the motion of the car matches the motion of the wind, you’re likely to at least feel that turbulence.
Yes, but you will defintely feel the difference between that and driving the other direction.
The turbulence is due to the car moving trough the air. If the car and the air move at the same speed, the car causes no turbulence. Of course, ordinary wind is not turbulence free, so you might feel that.
How is the car “passing through” the air if they are traveling at the same speed?
In the ideal case where there was no boundary layer at the ground and the profile of the wind speed was an exact, constant 30 mph right down to the ground, it would be no different than if the car was standing still on a calm day. Of course, the real world is not ideal and the wind speed would not be constant or uniform, which would lead to some buffeting.
Disregarding the inaccuracy of the instruments involved, you won’t feel anything. You also won’t use much gas. The only thing the engine would have to overcome is the friction of the wheels, ground, and internal components of the car. If those weren’t present (i.e. you were in an glider or balloon), then you’d move with the wind at the wind’s speed.
I guess if the wind was completely level even to the ground, and there were no gusts, you wouldn’t feel anything except maybe the tires hitting the air at a net 30mph.
But there is always a difference between ground airspeed and air airspeed, so the bottom of the car is probably going to interact with the air anyway. Not sure if your arm would feel it or not.