7 Fun Demos of Bernoulli’s Principle Explained

Summary

In this educational video, the presenter explores Bernoulli's Principle through seven engaging demonstrations. The principle, which states that an increase in fluid speed leads to a decrease in pressure, is illustrated with practical examples like paper strips, soda cans, ping pong balls, and even a beach ball. Each demonstration highlights how fluid dynamics create pressure differences that can result in lifting or suspending objects, such as an airplane wing's lift. Despite air being a compressible fluid, the demonstrations effectively showcase Bernoulli’s Principle in action, making it both a fun and educational experience.

Takeaways

• 😀 Bernoulli's equation relates fluid pressure, speed, and height, stating that the total of these factors is constant at different points in a fluid.
• 😀 Bernoulli's Principle explains that an increase in fluid speed leads to a decrease in pressure.
• 😀 The demonstrations simplify Bernoulli’s equation by assuming that height differences are negligible compared to speed and pressure differences.
• 😀 Although air is compressible and not an ideal fluid, Bernoulli’s Principle still holds true in most real-world scenarios.
• 😀 The first demonstration shows how blowing air over a strip of paper creates an upward pressure difference, causing the paper to lift.
• 😀 The principle of lift on an airplane wing works similarly: faster-moving air over the top of the wing creates lower pressure than below, causing lift.
• 😀 In the second demonstration, blowing air between two cans causes the cans to move towards each other due to lower pressure between them compared to the outside air.
• 😀 The third demonstration involves a ping pong ball in a funnel. Blowing air through the funnel causes the ball to be pulled towards the funnel due to pressure differences.
• 😀 The fourth demonstration flips the funnel, blowing air downward, creating an upward pressure difference that suspends the ping pong ball in the funnel.
• 😀 The fifth demonstration shows that a ping pong ball can be suspended in a stream of air from a straw, as pressure differences on either side keep it in place.
• 😀 The sixth demonstration uses a leaf blower and a beach ball, showing how the faster-moving air above the ball creates lower pressure, suspending the ball in mid-air.
• 😀 The seventh demonstration amplifies the first by using a leaf blower to blow air over a roll of toilet paper, which is lifted by the pressure difference created by faster air above it.

Q & A

What is Bernoulli's equation?

Bernoulli's equation states that for a fluid, pressure plus one-half of the fluid density times fluid speed squared plus the fluid density times gravitational field strength times vertical height is constant. In other words, these variables at one point in the fluid are equal to those at another point in the fluid.

Why are height differences neglected in the demonstrations of Bernoulli's Principle?

In the demonstrations, height differences are considered negligible because the variations in speed and pressure are much larger than the changes in height. Therefore, the vertical height term in Bernoulli's equation is crossed out or neglected.

Why is air considered not an ideal fluid in these demonstrations?

Air is considered not an ideal fluid because it is compressible. However, despite this, Bernoulli's Principle still holds true, which states that an increase in speed corresponds to a decrease in pressure, even for air.

What causes the strip of paper to lift when a hair dryer blows air over it?

The faster-moving air above the strip of paper creates lower pressure above the paper, while the slower-moving air beneath the paper maintains higher pressure. This pressure difference causes the paper to lift upward.

How is Bernoulli's Principle applied to airplane wings?

The shape of an airplane wing causes air to move faster over the top of the wing than beneath it. This results in lower pressure above the wing and higher pressure below, generating lift and allowing the airplane to fly.

What happens when air is blown between two soda cans in the second demonstration?

Blowing air between the two soda cans increases the speed of air between them, which reduces the pressure between the cans. The higher pressure outside the cans pushes them towards each other.

Why does a ping pong ball tend to move towards the funnel when air is blown through it?

When air is blown through the funnel, the pressure below and to the sides of the ping pong ball is lower than the pressure above it. This pressure difference causes the ball to move toward the funnel.

What occurs when the funnel is turned upside down and air is blown through it?

When the funnel is turned upside down and air is blown through it, the air speed above the ping pong ball becomes higher than the air speed below it, creating an upward pressure difference that suspends the ball in the air.

How does the difference in air pressure help the ping pong ball stay suspended in the air when blown through a straw?

When the ping pong ball is in the stream of air from the straw, the faster-moving air on one side of the ball causes lower pressure, and the slower-moving air on the other side causes higher pressure. This pressure difference pushes the ball toward the stream of air, helping it stay suspended.

How does a leaf blower demonstrate Bernoulli's Principle with a beach ball?

When the air from the leaf blower is directed over the top of the beach ball, the air speed above the ball is faster than below it, resulting in lower pressure above the ball and higher pressure below. This causes the ball to be suspended in the air, just like the ping pong ball with a straw.