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Bernoulli's Principle
Bernoulli's Principle
BERNOULLI'S PRINCIPLE states that pressure decreases as velocity increases. In this case, blowing on a straw in between the two ping pong balls increases the speed of air which lowers the pressure. This causes the two balls to collide since the outside becomes higher pressure, pushing them together.
Magnus Effect
Magnus Effect
The Magnus Effect is the force exerted on a rapidly spinning object moving through air or another fluid in a direction that is at perpendicular to it’s spinning axis. This is a simple demonstration that you can do with a piece of paper and a clipboard/cardboard. As the cylinder is rolling down the board, because a greater pressure is created on the side away from me (look at the visual near the end). The greater pressure is created when there’s lower wind speed, which is the result of Bernoulli’s Principle. Look at the post before this to learn more about Bernoulli’s Principle. Stay tuned for next Thursday to see another example of the Magnus Effect.
Does the type of paper matter?
Yes! I wanted to use a light blue paper to give a better visual. However, I noticed that the lined sheet of paper had a better curve. Since the lined paper was lighter, it had a better lift.
I purposely placed the ding sound effects to point out what materials I was using. The styrofoam cups form a larger loop and gets more lift do to its lightness. However, the plastic cups provides a longer flight path; tiny plastic cups work really well for this case.
PART 1: This is another great demonstration of the Magnus Effect, which is the force exerted on a rapidly spinning object moving through air or another fluid in a direction that is at perpendicular to it’s spinning axis. In this case, a rubber band is wrapped around the cups and pulled back. When I release it, the cups travel forward while curving upwards. Come back tomorrow to see how you can make one yourself!
What if you use large popcorn barrels? Check out Bruce Yeany’s “Physics it Toys- Cup Flyers” to see! He also has other fantastic trials.
The Magnus Effect is affected by the Bernoulli’s Principle. The greater pressure is created when there’s lower wind speed. Check out my ping pong demonstration (2 posts before this) for more details on Bernoulli’s Principle.
PART 2: A super easy project that you can recreate on your own! Try using cups that are different in materials and diameters to vary the flight path. Check out the last post to see the flying cups in action and the physics behind the Magnus Effect!!
Breaking Board Paradox
Breaking Board Paradox
So why does the board only break when the newspaper is laid out? This video deals with three things: Newton’s first law, second law, and of course air pressure. The wood plank does not have much inertia, due to its small amount of mass. The newspaper also does not have much mass either.
The newspaper that I used was 528 inches squared (24 by 22). We know that air pressure is 14.7 pounds per square inch against every surface. Therefore we multiply 528 inches squared by 14.7 PSI to get 7,762 pounds. There is 7,762 pounds being applied onto the wooden board when we apply the newspaper!! You cannot feel 7,762 pounds but the newspaper does restrict the board from moving.
Try doing this experiment with a smaller width plank, the plank will give a completely different result!! Hint: you get better results with bigger boards. Think about what the amount of area of the board means.
Archimedes Principle and Buoyancy Force
Archimedes Principle and Buoyancy Force
This Cartesian Diver demo can be easily created. It is a great illustration of Buoyancy Force and Archimedes Principle. Archimedes Principle is ”when a body is immersed fully or partially in a fluid (gas or liquid), it experiences an upward force that is equal to the weight of the fluid displaced by it.” In other words, the upward force equals the weight of the liquid displaced. Liquid displacement is calculated by the real weight minus the apparently weight. That upward force that is exerted by a fluid (contradicting the applied force) is called Buoyant force. The buoyant force supports objects that are less dense than the fluid. Due to these two reasons, the bottle must be capped.
When the bottle is squeezed, smaller air bubbles are made due to the water being forced into the straw. The squeezing also causes the air to be compressed allowing the straw to be less buoyant; therefore, it sinks down since it’s not greater than the force of gravity. When the bottle is released, the opposite happens. The bouyant force becomes greater than the force of gravity so the straw floats.
This video reveals how only one can sink down while the other ones stays afloat. Since the white straw is made with a lighter material, putting more weight onto the straw would solve the problem. This experiment also allows you to figure out what the correct amount of weight is needed to make the Cartesian Diver. Through out my tests, I found that two small paper clips and one bigger paper clip was just the right amount of weight. Make sure you check out last description to understand the physics of the Cartesian Diver even further.
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