Demonstrate the Bernoulli Principle using straws and two empty soda cans
Named after Daniel Bernoulli, the Bernoulli Principle states that as a fluid’s velocity increases, a pressure decrease occurs. The mathematician Daniel discovered many new ideas regarding fluids and pressure. For instance, Bernoulli, who had begun to study medicine, wanted to know about the relationship between the blood flow rate and its pressure. He poked a hole in a pipe, stuck a straw in it, and noticed that when the fluid sped up, the liquid rose higher in the straw. Soon doctors all over Europe were poking holes in patients’ arms and sticking little glass tubes in them to test their blood pressure. Ouch! This practice continued for nearly 200 years until an Italian doctor discovered our modern method of measuring blood pressure.
- Place 30 to 40 straws next to each other on a flat table. Leave about ½ inch space in between them.
- Place the two empty soda cans on the straws so that they can roll back and forth on the straws. Leave about 1 inch of space in between the cans.
- Take a straw and blow air through it in between the two cans.
You may have thought that by blowing air between the cans they would spread apart but the opposite actually happens – the cans move closer together. This occurs because the air’s velocity (or speed) between the cans increases when you blow between them with the straw. Bernoulli’s principle states that as the velocity increases, the pressure decreases. The lesser pressure between the cans causes them to move towards each other.
The Bernoulli Principle – advanced notes
The Bernoulli principle states that as the speed of a fluid (gas or liquid) increases, its pressure decreases. This principle was first formulated by the Swiss mathematician, Daniel Bernoulli in 1738. The principle is used to explain the lift generated by an airplane wing, the working of a carburetor, and the behavior of fluids in pipes.
According to the Bernoulli principle, the higher the speed of a fluid, the lower its pressure. This is because the fluid molecules move faster when the speed is higher, and this reduces the amount of time they spend in any given area. As a result, there are fewer molecules pushing against any given surface, which leads to a decrease in pressure.
The Bernoulli principle has many practical applications. For example, it is used in the design of airplane wings. The wing of an airplane is designed to be curved on its upper surface and flat on its lower surface. When air flows over the wing, it travels faster over the curved upper surface than over the flat lower surface. This creates a difference in pressure between the upper and lower surfaces of the wing, which generates lift and enables the airplane to fly.
Required supplies for the Bernoulli’s Principle science experiment
Supplies: Straw, Soft drink can
In-Article Image CreditsVenturi tube with labels via Wikimedia Commons with usage type - GNU Free. September 14, 2004
An illustration of the incorrect equal transit-time explanation of airfoil lift via Wikimedia Commons with usage type - Creative Commons License. March 27, 2019
Featured Image CreditAn illustration of the incorrect equal transit-time explanation of airfoil lift via Wikimedia Commons with usage type - Creative Commons License. March 27, 2019