2.6 Application of Bernoulli’s Principle
Aeroplane
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- When a wing in the form of an aerofoil moves in air, the flow of air over the top travels faster and creates a region of low pressure. The flow of air below the wing is slower resulting in a region of higher pressure.
- The difference between the pressures at the top and underside of the wing causes a net upward force, called lift, which helps the plane to take-off.
Q & A
Q: Explain how an upthrust is produced when the aeroplane is moving.
A:
- When the aeroplane is moving, air flows faster above the wing than below.
- Therefore, the air pressure below the wing is higher than above.
- The difference in air pressure produces a net force acting upwards.
Q & A
Q: There are slat in front and flaps at the back of the wings of an aeroplane. Describe with the aid of a diagram how the slat and flaps of the wings help in lifting the aeroplane when the aeroplane starts to depart.
A:
- When the aeroplane starts to depart, the slat and flaps are stretched and spread out to increase the surface area of the wings.
- This increases the lifting force acting on the aeroplane.
Sports
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In some of the sport such as football, a player can make the ball move in a curve path by spinning the ball. This effect can be explained by Bernoulli’s Principle.
Insecticide Spray
- When the plunger is pushed in, the air flows at a high velocity through a nozzle.
- The flow of air at high velocity creates a region of low pressure above the metal tube. The higher pressure of the atmospheric air acts on the surface of the liquid insecticide causing it to rise up the metal tube.
- The insecticide leaves the top of the metal tube through the nozzle as a fine spray.
Bunsen Burner
- When the burner is connected to a gas supply, the gas flows at high velocity through a narrow passage in the burner, creating a region of low pressure.
- The outside air, which is at atmospheric pressure, is drawn in and mixes with the gas.
- The mixture of gas and air enables the gas to burn completely to produce a clean, hot, and smokeless flame
Carburetor
A carburetor is a device that blends air and fuel for an internal combustion engine. Figure above shows how Bernoulli’s principle is applied in a carburetor to mix the air with the fuel.
Q & A
Q: Explain why 2 fast moving boats tend to move closer to each other.
A:
- When the two boats travel at high speed, the stream of fluid (air and water) between the boats flow faster than the other sides of the boats.
- This form a low pressure zone in between the boats.
- The higher pressure at the other sides of the boat pushes the boats closer to each other.