A plane is in level flight at constant speed and each of its two wings has an area of 40 m2. If the speed of the air is 180 km/h over the lower wing surface and 252 km/h over the upper wing surface, the mass of the plane is kg. (Take air density to be 1 kg m-3 and g = 10 m s-2)
Answer
9600
Solution
v1 = 180 km/h = 50 m/s, v2 = 252 km/h = 70 m/s
Bernoulli (same level): P = 12 (v22 - v12 )
= 12(1)(4900 - 2500) = 1200 Pa
level flight: lift = weight mg = P (2 40)
m = 1200 8010 = 9600 kg
Answer: 9600