Question

The lifting force, F, exerted on an airplane wing varies jointly as the area, A, of the wing's surface and the square of the plane's velocity, v. The lift of a wing with an area

of 280 square feet is 27,800 pounds when the plane is going 220 miles per hour. Find the lifting force on the wing if the plane slows down to 130 miles per hour.
(Leave the variation constant in fraction form or round to at least 5 decimal places. Round off your final answer to the nearest pound.)

Answer 1

If the lifting force varies jointly with wing surface area and the square of the plane's velocity, then:

F = kAv²

If the lift is 27,800 pounds when the area is 190 sq. ft and the velocity is 230 mph, then the constant of proportionality is:

27,800 = k(190)(230)²

k = (27,800) / (190)(230)² = 139/50255

The lifting force the plane slows down to 200 mph is:

F = (139/50255)(190)(200)²

F = 21,020.79

Rounded to the nearest pound, the lifting force is 21,021 pounds.