**BERNOULLI'S**

PRINCIPLE

PRINCIPLE

"A phenomena named after the Swiss scientist Danielle Bernoulli" [12]

"A Swiss doctor, mathematician and physiscian, (1700-82), who is most prominent for his applications of mathematics to mechanics particularly fluid mechanics" [12]

How can one measure blood pressure?

Danielle worked with Leonhard Euler (also a Swiss scientist) to investigate the relationship between the speed of the blood flow and its pressure. [6]

For the investigation, Danielle punctured a small hole in the wall of a pipe with an open-ended straw and he observed that the height to which the liquid flowed in the straw was the pressure of the fluid in the pipe. And that became a method of measuring a person's blood pressure (simply inserting straws directly into a persons arteries. [6]

When Danielle went back to his work on Conservation of Energy which states that for an isolated system, the total amount of energy remains constant overtime. For instance, energy can be changed from one form to another but it cannot be created or destroyed. Danielle knew that as an object gains height, its kinetic energy changes to potential energy. So he realized that the kinetic energy in a constant fluid flowing system is exchanged for pressure. [6]

Taking it further

The Bernoulli Equation can be considered to be a statement of the conservation of energy principle appropriate for flowing fluids. The qualitative behavior that is usually labeled with the term "Bernoulli effect" is the lowering of fluid pressure in regions where the flow velocity is increased. This lowering of pressure in a constriction of a flow path may seem counterintuitive, but seems less so when you consider pressure to be energy density. In the high velocity flow through the constriction, kinetic energy must increase at the expense of pressure energy. the pressure in sector T was more which means the kinetic energy (i.e the speed of the fluid) was low and for sector t of the pipe, the pressure was low and so the speed of the fluid was high. We can see this phenomena clearly in the pipe below. The pressure and velocity measuring device is place in three different locations(shown in the diagram below) and if we observe closely, we see that the pressure and velocity readings change as the water flows from a wider sector of pipe to a narrower sector. [6] [9] [5]

the result

Interesting

Facts

Due to the pressure difference, the air particles move from an area of high pressure (i.e. the bottom of wing) to an area of low pressure (i.e. the top of wing) resulting in a push on the wing which is known as the lift. [2] [7] [1]

Bernoulli's principle in aviation

How it works

Ever wondered that how

a curved ball curves

in a baseball game?

Bernoulli's principle can be used to explain how an aircraft wing lifts. The wing of an aircraft is shaped in such a way that a force acting on the wing causes it to lift up. The top of the wing is longer than the bottom and since the time for air to pass from the wing's top and bottom would be the same. So the speed of the air at the top of the wing would be high, which means low pressure and the speed of the air at the bottom of the wing would be low, high pressure. [2] [7] [1]

Bernoulli's Principle!

How?

When a pitcher throws a curve ball, the ball curves in the direction of the spin, so for the ball to curve to the left, the pithcer must spin the ball anti-clockwise and for the ball to curve to the right, the spin on the ball must be clockwise. [3]

If we look at the example on the left, we can see that the ball is thrown forward which means that, relative to the ball, the air is moving backwards. Also, the spin on the ball is cloockwise and when the ball spins the wind adjacent to the ball moves with the ball. The wind to the left of the ball is moving against the normal flow of air and so it's speed would be reduced. Whereas, the air on the right of ball flows in the same direction as the air flow. So the speed of air on the right side of the ball would have higher speed than the air on the left side of the ball. Which means that the left side has high pressure than the right side and so the ball moves away form the straight line and curves to the right (High pressure to low pressure). [3]

**The End**

Work cited:

1.

Bernoulli's principle. (n.d.). Retrieved from http://www.scienceclarified.com/everyday/Real-Life-Chemistry-Vol-3-Physics-Vol-1/Bernoulli-s-Principle.html

2.

Fun science and technology for kids. (2011, December 08). Retrieved from http://www.sciencekids.co.nz/lessonplans/flight/flightintroduction.html

3.

Martin, M. M. (1997, February 5). The physics of baseball. Retrieved from http://www.stevetheump.com/HR_physics.htm

4.

Physclips. (n.d.). Retreived from http://www.animations.physics.unsw.edu.au/mechanics/chapter7_energyandpower.html

5.

Pike, J. (n.d.). Background, development, and theory. Retrieved from http://www.globalsecurity.org/military/library/policy/army/fm/1-506/Ch2.htm

6.

Quinney, D. A. (1997). Daniel Bernoulli and the making of the fluid equation. Retrieved from http://plus.maths.org/content/daniel-bernoulli-and-making-fluid-equation

7.

Rutkowski, T. (n.d.). May the force be with you: Lift. Retrieved from http://www.teachengineering.org/view_lesson.php?url=http://www.teachengineering.org/collection/cub_/lessons/cub_airplanes/cub_airplanes_lesson02.xml

8.

What is kinetic energy? (2010, July 19). Retrieved from http://physicsindaytodaylife.blogspot.com/2010/07/what-is-kinetic-energy.html

9.

William, S. (n.d.). Bernoulli’s principle. Retrieved from http://aviationglossary.com/aircraft-terms-definition/bernoullis-principle/

10.

Winnipeg. (1999, September 29). Retrieved from http://theory.uwinnipeg.ca/mod_tech/node68.html

11.

Centre interfacultaire bernoulli - lausanne. (n.d.). Retrieved from http://cib.epfl.ch/poisson2008/index.html

12.

artdirectory. (2011). Retrieved from http://www.daniel-bernoulli.com/

From the video we can see that when the ball is placed in front of the air blower, the ball remains suspended in the air. How? That happens because of Bernoulli's principle. The ball is placed in an area where the speed of air is high (due to the air blower) and the area to the left and right of the ball has lower speed. Which means that in the area of the ball, the pressure is lower comapared to the sides. So if the ball tries to move left or right, the high pressure on both sides would keep the ball in the area of low pressure (i.e. because air moves from area of High pressure to an area of low pressure) [4]

Figure 6: Curve ball physics [3]

Figure 1.0: Danielle Bernoulli [11]

Figure 2.0: Bernoulli's diagram to illustrate how pressure is measured. [6]

Figure 3.0: Bernoulli's principle- Venturi tube [9]

Figure 4.0: Bernoulli's Principle demonstrated on an airplane wing. [7]

Figure 5.0: How a wing produces lift. [7]

Figure 7.0: Floating ball [4]

Bernoulli's Blower