A horizontal stream tube of air of cross-section and speed approaches an aircraft…

PHYSICS · Single correct · AP · Physics 1: Algebra-based · Fluids · Fluids

Problem

A horizontal stream tube of air of cross-section

1.0\,\text{m}^2

and speed

25\,\text{m s}^{-1}

approaches an aircraft wing and splits into two parts. Over the upper surface the cross-section contracts to

0.40\,\text{m}^2

, while under the lower surface it widens to

0.60\,\text{m}^2

. If air density is

1.2\,\text{kg m}^{-3}

and the wing planform area is

3.0\,\text{m}^2

, what is the lift force on the wing? (a)

5.9\,\text{kN}

(b)

3.9\,\text{kN}

(c)

1.3\,\text{kN}

(d)

2.6\,\text{kN}