Experiments
Illustrating
Bernoulli's Principle
Below are three simple experiments illustrating Bernoulli’s principle.
Bernoulli’s principle is a fundamental concept in fluid dynamics that provides insight into the relationship between the velocity and pressure within a fluid in motion.
Ball Defies Gravity
Please watch this video. Can you explain why the ping pong ball remains inside the funnel, even when the funnel is nearly inverted?
The ping pong ball remains suspended while the air compressor is operating and directing air through the funnel. When the compressor stops, the ball drops immediately.
What is going on? This demonstrates Bernoulli’s principle.
According to Bernoulli’s Principle, the fast-moving fluid (air in this case) has low-pressure compared with its surroundings.
The rapid movement of air through the funnel produces a low-pressure region around the ball. The air beneath the ball, which is at higher pressure, moves upward toward this low-pressure area, resulting in the ball being supported.
When the air flow ceases, the pressure difference is eliminated, and the air does not move upward. At this point, gravity causes the ball to descend.
Also please take a look at the next video which shows a ping pong ball suspended in fast-moving stream of air.
Ball Floats in Air
Please watch this video. What causes the ping-pong ball to remain suspended in the stream of air produced by the hair dryer?
This again demonstrates Bernoulli’s principle: fast-moving air from the hair-dryer lowers the pressure around the ball. Air below, at normal pressure, moves up into the low-pressure area, keeping the ball suspended.
Ball Stuck in Funnel
Observe the video carefully: the ping-pong ball remains lodged at the base of the funnel as long as water continues to flow through it. Once the water flow ceases, the ping-pong ball rises to the surface.
This exemplifies Bernoulli’s principle. As water moves rapidly through the funnel, it generates a region of low pressure around the ball. This lower pressure causes the water above the ball to move toward the area surrounding it, thereby maintaining the ball’s position at the bottom.
When water flow stops, the pressure gradient disappears, causing the water above the ball to stop moving downward. At this stage, buoyancy acts to lift the ball upward.
Takeaways
As discussed above, these three experiments serve as classic illustrations of the elegance underlying Bernoulli’s principle.
Discovered in the 18th century by Daniel Bernoulli of Netherland, Bernoulli’s principle continues to influence a vast array of fields, from engineering to medicine, architecture, and beyond.
Whether in the lift of an airplane wing, the spin of a soccer ball, or the flow of medicine in a nebulizer, Bernoulli’s principle reminds us of the elegance and interconnectedness of the physical world.