Showing posts with label Bernoulli. Show all posts
Showing posts with label Bernoulli. Show all posts

January 6 – Happy Birthday, Jacob Bernoulli

Posted on January 6, 2015

Jacob was one of eight gifted mathematicians in his family (and the first)! Born in Switzerland on this date in 1655, he so loved the logarithmic spiral, he asked that it be carved on his gravestone, which was erected after his 1705 death.

In between his birth and death, Jacob Bernoulli made many contributions to calculus, but he is most famous for his work on probability.

Here are some of the things that Bernoulli explored, discovered, and made contributions to:
You probably know that infinity is endless. Well, an infinite series is the sum of infinitely many numbers related to each other in a particular, defined way. Here is an example:

1/2 + 1/4 + 1/8 + 1/2^n

As n gets larger and larger, the fraction ½  to the nth power gets smaller and smaller, and although it seems that you can never QUITE get to the number 1, since there are an infinite number of fractions added to the series, we say that the answer converges on 1.

By the way, infinite series are important in practical fields such as engineering and biology!


This important number is approximately 2.71828 but it is irrational, so the digits after the decimal place go on and on and on and on...forever! Although it seems impossible that this number would be important in any way, Bernoulli discovered it when studying compounding interest (something that banks do so that you can grow your money!).






A differential equation states how a rate of change in one variable is related to other variables.


Probability is simply the likelihood of something happening. You can explore probability using dice, cards, spinners, or colored M&Ms. 

Here are some simple questions you can ask (there are way more complicated questions!):

  • If you throw one die ten times, what percent of the time will you roll a 6? How about if you throw the die ten thousand times?

  • In the game 21, if you have 11 points and want to get to 21, how likely are you to get 10 points in your next card? (Face cards AND the ten-spot cards are all worth 10 points.) Obviously, it depends on how many 10's have already been played!

  • If there are 30 spots on the spinner, alternating black and red, what is the likelihood of spinning a red?

  • What is the likelihood of pulling out a brown M&M from a full bag of M&Ms?

Here is a really interesting probability problem called the Monty Hall Problem.



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February 8, 2012 - Happy Birthday, Daniel Bernoulli



How did studying the speed of blood flow and blood pressure help us design airplanes?

Dutch-Swiss mathematician and scientist Daniel Bernoulli (born on this date in 1700) observed and tested the flow of fluids, that is, liquids and gases. He tried to understand how the speed of blood flow in veins and arteries related to the pressure it exerts. To find out, he punched holes in pipes and inserted vertical straws, and then he measured the height to which the fluid rose up the straw. Here's what he found:


The quicker the motion of fluid in the pipe, the less the pressure exerted, and the lower the level of fluid in the vertical straw. When fluid moves at lower speeds, it exerts more pressure and pushes up into the straw to a higher level. Bernoulli was able to devise mathematical equations to match his experimental findings.

Here is an animation you can manipulate to see the difference in speed-of-motion (velocity) and pressure, depending on the shape of a pipe. Be sure to “grab” and “drag” the little yellow boxes to change the shape—then check out the graphs below that show the relation of the speed to the pressure. Make really exaggerated shapes with a really narrow mid-portion, for example, and one very wide end, to see the results most clearly. 

Apparently, for more than a century, based on Bernoulli's findings, doctors measured blood pressure by sticking point-ended glass tubes directly into people's arteries. Eeek! I feel glad that a less invasive and painfully method was eventually invented!

Later on, airplane wings were designed to take advantage of Bernoulli's principle—with the air moving more quickly over the top of the wing, creating less pressure—and therefore providing lift as the greater pressure under the wing pushes the wing up.

Bernoulli's fluid mechanics have been used in many other ways, of course; also, Bernoulli made other contributions to mathematics, statistics, and science. So hooray for Bernoulli!


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