Home Physics The Bernoulli Ghost - The Physics Behind It

# The Bernoulli Ghost – The Physics Behind It

Last updated on November 12th, 2020 at 09:41 pm

The Swiss mathematician and physicist, from a family full of prominent mathematicians, Daniel Bernoulli discovered the principle that bears his name while conducting experiments concerning an even more fundamental concept: “The Conservation of Energy”.

## The Bernoulli Principle

The principle states that ideally for a fluid, the pressure is inversely related to its velocity. In other words, a slow-moving fluid exerts higher pressure whereas a fast-moving fluid exerts a lower pressure on the walls. Although the breakthrough was done by Bernoulli that pressure and velocity are inversely related but the formalization of Bernoulli’s equation in its usual form was done by Leonhard Euler.

## A Human Analogy

You go out to watch a movie in the cinema hall. After the show is over, there is a “high pressure” near the exit doors and hence the crowd “slows” down. Once having passed the doors, the “pressure is low” and people resume their original “faster” speed.

## A Spinning Baseball

Baseball is an example of where Bernoulli’s principle is very visible in everyday life. One example in baseball is in the case of the curveball. The entire pitch works because of Bernoulli’s principle. Since the stitches of the ball actually form a curve, it is necessary for the pitcher to grip the seams of the baseball. The reason as to why this is a necessity is that by gripping the baseball this way, the pitcher can make the ball spin. This allows for more air pressure on the top of the ball and less air pressure on the bottom of the ball. Therefore, according to Bernoulli’s principle, there should be less speed on the top of the ball than there is on the bottom of the ball. The result is that the bottom part of the ball accelerates downwards faster than the top part, and this phenomenon allows for the ball to curve downward, which causes the batter to miscalculate the ball’s position.

## A Flying Airplane

Another one of the most common everyday applications of Bernoulli’s principle is in air flight. The way that Bernoulli’s principle works in air flight has to do with the architecture of the wings of the plane. In an airplane wing, the top of the wing is somewhat curved, while the bottom of the wing is totally flat. While in the sky, air travels across both the top and the bottom concurrently. Because both the top part and the bottom part of the plane are designed differently, this allows for the air on the bottom to move slower, which creates more pressure on the bottom, and allows for the air on the top to move faster, which creates less pressure. This is what creates lift, which allows planes to fly. An airplane is also acted upon by a pull of gravity in which opposes the lift, drag, and thrust. Thrust is the force that enables the airplane to move forward while drag is air resistance that opposes the thrust force.

## The Invisible Pushing Ghost

Your parents may have cautioned you several times to stand away from the railway tracks as a fast train whizzes by. You experience a loud roar if you do so, but there is a physical reason behind it. It is the Bernoulli’s law. The air between the tracks is dragged along with a high speed and hence has lower pressure by Bernoulli’s principle. The atmosphere behind the curious bystander is stationary and has higher pressure as above. Thus, there is a net pressure pushing you towards the train.

So next time you know that all those ghostly incidents were because of the Bernoulli Principle.

There is no philosophy which is not founded upon knowledge of the phenomena, but to get any profit from this knowledge it is absolutely necessary to be a mathematician.” ~ Daniel Bernoulli

Video Courtesy: India Wild Films

References: Physics and the city of MUMBAI – Prof. Vijay Singh

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##### Akshat Mishra

Akshat Mishra is currently pursuing his doctoral degree in Physics from Lund University in Sweden. He feels the need to explore the depths of the not-so-dark universe while at the same time watch the quanta in action. Electronic Music is what puts him in the thinking zone.

Akshat Mishrahttps://www.scilynk.in/akshat-mishra
Akshat Mishra is currently pursuing his doctoral degree in Physics from Lund University in Sweden. He feels the need to explore the depths of the not-so-dark universe while at the same time watch the quanta in action. Electronic Music is what puts him in the thinking zone.

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