A plane is in level flight at constant speed and each of its wings has an area of 25 m2. If the speed of the air is 180 km/h over the lower wing and 234 km/h over the upper wing surface, determine the plane’s mass. (Take air density to be 1 kg/m3), g = 9.8 m/s2
The area of the wings of the plane, A=2×25=50sq−m Speed of air over the lower wing, V1=180km/h=50m/s Speed of air over the upper wing, V2=234km/h=65m/s Density of air, =1kg/cu.m Pressure of air over the lower wing =P1 Pressure of air over the upper wing =P2 The upward force on the plane can be obtained using Bernoullis equation as: P1−P2=21ρ(V22−V12) F=(P1−P2)A=21ρ(V22−V12)A F=(P1−P2)A=21×1×(652−502)×50=43125N ∴m=gF=4400kg
