1. Venturimeter: This device is used to measure velocities and mass rate of flow of liquid at the different cross-sections of a pipe. it consists of a constriction inserted in a pipe line and have tapers at the in let and outlet, so that turbulence is avoided. (See fig.)
Let at the cross-sectional areas A1 and A2, the velocities are v1 and v2 respectively.
From the equation of continuity,
A1v1 = A2v2
From Bernoulli's theorem,
2. Blood flow and heart attack: When on the inner walls of any artery, layer of cholesterol and calcium salt if deposited, its inner diameter decreases i.e.; the artery becomes narrower. To maintain the blood flow in this narrow pact the pressure on the blood should be increased. To increase this pressure the cardiac muscles apply more than normal pressure to push the blood out of the heart. As a result the blood flow in this narrow part increases and from Bernoulli’s principle the pressure in the artery decreases. Thus, in this condition the pressure on the wall of the artery from inside is lesser than the pressure from the outside. So the artery contracts and closes.
In this condition Bernoulli’s principle does not apply. Due to pressure applied by the heart on the blood the artery opens again, when blood flows in this constricted part then velocity being more, pressure reduces further and the artery closes again. Now if the deposited layer moves from its place and goes to a smaller blood vessel carrying blood to the heart and blocks it then it leads to heart attack.
3. Magnus Effect: When a cricket ball is thrown spinning, the air velocity below it becomes more than that on the above. The pressure above it becomes more than that below it. So a resultant force acts on it and hence, the path becomes curved. This effect is called Magnus effect. In other words, Magnus effect is the difference in lateral pressure that causes a ball to take a curved path which is convex towards the greater pressure side.
4. Still water runs deep: The static pressure of deep water is more. So, from the Bernoulli’s principle, the speed of water is less due to more pressure and hence, the water is still.
5. During the arrival of train on the platform, the person standing on the platform bends forward because the velocity of air increases and air pressure decreases due to the fast speed of the train. The air pressure behind the person is more.
6. Atomizer: An atomizer consists of a vessel A containing the liquid which is to be sprayed. Vessel A is connected to a rubber bulb through a tube B.
When we press the rubber bulb, air rushes at N. According to Bernoulli’s theorem, low pressure is created near N. The liquid from A rises to B, to compensate the loss of pressure. If we further push the rubber bulb, the liquid comes out from N in the form of fine drops.
7. Pitot Tube: It is based on Bernoulli’s theorem, it is used to determine the velocity of the fluid. It is basically a U-tube which is shown in the figure. Its X-end is narrow and here velocity of the fluid is zero. It is called as stagnation point. From Bernoulli’s principle, for point X and Y
8. Bunsen Burner: In a Bunsen burner, the gas goes out with a great velocity from a fine nozzle. The pressure falls sufficiently below the nozzle and to compensate this decrease, air rushes out from the hole made at the side of the tube. So, air gets mixed with gas and burns.
9. Aerofoil Shape: Bernoulli’s principle is used in designing the shape of wings of aircraft. The curvature on the upper side of the wings is more than that on its lower side and its portion on the back is flat while the portion on the front is round.
Due to this type of shape of the wings, the velocity of the layers of air on its upper side is more than that on its lower side. Also, the pressure below is more which helps in lifting the plane up and simultaneously pushes it in the forward direction.
