When we blow air over a strip of paper as shown in the above figure, we find that the paper moves up. This is because, on blowing air, the velocity of air increases, creating low pressure above the paper and high pressure below the paper. This difference in pressure, lifts the paper
The working of spray-gun is based on Bernoulli's theorem
When the rubber bulb is squeezed, air is blown into the tube A, due to which, low pressure and high velocity is created. Since this pressure is less than the atmospheric pressure, the liquid is pushed up. This rising liquid is sprayed out of the nozzle 'N', due to the blowing air.
The wings of an aeroplane are designed such that the upper surface has a greater curvature than its lower surface. As the aeroplane moves, the air blows in the form of streamlines. The air travels a longer distance over the upper surface when compared to distance to its lower surface, in a given time. This creates a difference in the velocity of the air above and below, as shown. The pressure at top of the wing is low and below the wing is high. This pressure difference gives it an additional thrust.
Sub Topics
Know more
Back to Top
- In a streamline tube, there are numerous streamlines. The velocity of flow increases when the streamlines come close to each other and decreases as the streamlines move away from each other.
- Lord Rayleigh observed that, when a sphere or cylinder moves in still air while spinning about an axis perpendicular to the direction of its motion, its curved path is more curved than when it is moving without spin. This is called the Magnus effect. This effect plays an important role in Tennis and Cricket.
If ball moves from left to right and topspins in the clockwise direction, according to Bernoulli's theorem, the force due to the pressure difference acts in the direction of gravity and so, the pitch curves more sharply, thereby, shortening the flight.
