A plane is in level flight at constant speed and each of its two wings has an area of 25 m2. If the speed of the air on the upper and lower surfaces of the wing are 270 km / h and 234 km/h respectively, then what must have been the mass of the plane? (Take the density of the air = 1 kg m-3)

Let v1,v2 are the speed of air on the lower and upper surface S of the wings of the plane P1 and P2 are the pressure there,According to Bernoulli's theoremP1+12ρv12=P2+12ρv22P1−P2=12ρv22−v12 Here, v1=234kmh−1=234×518ms−1=65ms−1v2=270kmh−1=270×518=75ms−1 Area of wings =2×25m2=50m2∴   P1−P2=12×752−652Upward force on the plane=P1−P2A=12×1×752−652×50mAs the plane is in level flight, therefor upward force balances the weight of the plane.∴mg=P1−P2AMass of the plane,m=P1−P2gA=12×1×752−65210×50=(75+65)(75−65)×502×10=3500 kg