Question

A 1-m long, thin symmetric airfoil is placed at a free stream. Calculate the drag force for the wind speed of 150 m/s. Assume that the average friction coefficient is C subscript D equals 0.002. A equals 3 space m squared, angle of attack is 0 to the power of degree.
A. 81
B. 162 N
C. 40.5 KN
D. 0 N

Answer 1

Answer:

A (81 N)

Explanation:

P = F/A, where P is the pressure on an object exerted by the force F over the area A. Using "D" to represent drag force specifically, this equation can be rearranged to D = CPA, where C is a constant of proportionality that represents the friction coefficient. The pressure exerted on an object undergoing motion through a fluid can be expressed as (1/2) ρv2, where ρ is the density of the fluid and v is the velocity by which the object is moving. Therefore, D = (1/2)(C)(ρ)(v²)(A).

V = 150 m/s, C(d) = 0.002, A = 3m², ρ(density  of air) = 1.2 kg/m3

Fd = (1.2 x 3 x 0.002 x 150²)/2 = 81 kg.m/s²

The drag force exerted on the airfoil is 81 N.