HOW THE JUMBO JET LIFTS UP?

When a heavy wind blows over a hut with thatched roof, the roof just blows up. When the air flows fast, the pressure drops. Hence air pressure decreases over the roof; the pressure under the roof becomes greater and it lifts off the roof. This is due to Bernoulli's principle.

Bernoulli's principle says, as the velocity of fluid increases, its pressure decreases. This principle is also used to measure human blood pressure.

When the planes runs very fast, the air flows fast over the wings and it flows slower under the wings. It happens because of the geometry of the wings. Hence there is more pressure under the wings and it lifts up the plane.

There is a formula for the lift of the plane.

L = 0.5*C*D*A*V^2

V- velocity of the plane.
A- area of the wing.
D- density of the air.
C- constant due to wing design.
L- lift

The Boeing 747- jumbo jet requires a lift of 2150000 N(upward force). This lift will cancel out the huge weight of the plane due to gravity and will keep the plane afloat.

Post script: Before the invention of mercury based BP measuring instrument, a capillary tube (very narrow tube) was directly inserted into the veins of the patient; blood rises into the tube to certain height indicating the pressure. This method was used for 200 years. Now we are experiencing non-invasive and painless measurement.

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