On a vacation flight, you look out the window of the jet and wonder about the forces exerted on the window. Suppose the air outside the window moves with a speed of approximately 140 m/s shortly after takeoff, that the air inside the plane is at atmospheric pressure and that the density of the air inside and outside the plane is 1.29 kg/m3.
(a) Find the pressure difference between the inside and outside of the window. (kPa)
(b) If the window is 25 cm by 33 cm, find the force exerted on the window by air pressure. (kN)

Question

On a vacation flight, you look out the window of the jet and wonder about the forces exerted on the window. Suppose the air outside the window moves with a speed of approximately 140 m/s shortly after takeoff, that the air inside the plane is at atmospheric pressure and that the density of the air inside and outside the plane is 1.29 kg/m3.
(a) Find the pressure difference between the inside and outside of the window. (kPa)
(b) If the window is 25 cm by 33 cm, find the force exerted on the window by air pressure. (kN)

anonymous · Answer

Still air pressure = Po.
Bernoulli equation, Po = P + (1/2) (rho) v^2.
Pressure on the window from air flowing past it will be
P=Po - (1/2) rho v^2, somewhat below atmospheric,
where rho is density of air and v is its velocity.

Force will be (Po-P) (A) pushing out on the window of area A (sq. meters).