drag force

[evusq]

The equation given is D=(1/2)CApV^2, where D is the drag force, C is a dimensionless value that depends on the car's shape, A is the effective cross sectional area of the car, and p is the density of air.
The question asks how the specific value of C varies with the aerodynamics; the answer given is that C decreases as the car's shape is made more aerodynamic.

I know that D and C are directly proportional, so the larger the value of C, the larger that of D. Since D is the air drag, doesn't higher D mean there's more aerodynamic? And if so, doesn't C get higher too? I'm so confused! Can someone explain this?

---

Members don't see this ad.

 

[PiBond]

High drag force is a result of a less aerodynamic car. As C increases (car becomes less aerodynamic) there's more drag force. The drag force is pointed in the opposite direction of velocity if you draw a free-body diagram.

Think of a ferrari driving down the road versus an H1 Hummer. The hummer (essentially a box on wheels) has a higher C value and thus a larger D (drag force). The ferrari is more aerodynamic and thus has a smaller C value and less drag force.

Just my 2 cents. Hope it helps.

 

[ezsanche]

Something that is aerodynamic experience little air drag.