# Leonard Euler

### Famous Scientist

## Childhood

Leonard Euler was born on April 15, 1707, in Basel, Switzerland. Though originally slated for a career as a rural clergyman, Euler showed an early aptitude and propensity for mathematics, and thus, after studying with Johan Bernoulli, he attended the University of Basel and earned his master's during his teens. Moving to Russia in 1727, Euler served in the navy before joining the St. Petersburg Academy as a professor of physics and later heading its mathematics division.

He wed Katharina Gsell in early 1734, with the couple going on to have many children, though only five lived past their father. The couple were married for 39 years until Katharina's death, and Euler remarried in his later years to her half-sister.

## How he became interested in Science

Leonhard Euler went to school in Basel, but the school was a rather poor one, and Euler learnt no mathematics. However his interest in mathematics had been sparked by his father's teaching, and he read mathematics texts on his own and took some private lessons. At age 14, he was sent to the University of Basel to prepare for the ministry. Johann Bernoulli soon discovered Euler's great potential for mathematics.

In 1723, Euler completed his Master's degree in philosophy, and began his study of theology in the autumn of 1723. He could not find enthusiasm for the study of theology, so he obtained his father's consent to change to mathematics after Johann Bernoulli had used his persuasion. Euler completed his studies at the University of Basel in 1726. He had studied many mathematical works during his time in Basel, including those by Varignon, Descartes, Newton, Galileo, von Schooten, Jacob Bernoulli, Hermann, Taylor and Wallis.

## Hardships

In 1735, while Leonard Euler was in St. Petersburg, he lost sight in his right eye. This is why Frederick called him a “mathematician Cyclops”. 25 years later, Euler lost sight in his left eye. This caused him to be completely blind from 1760-1789. This didn't prevent Euler from continuing to learn, because he simply did math in his head and continued to dictate many papers and books while blind.

## Contributions

The scientist Leonhard Euler, who was born in Basel and later moved to St. Petersburg is famous for his work in the field of mathematics. Less is known about his important contributions in the field of friction physics. He studied theoretically the mechanism of the sliding motion of a block on an inclined plane. He adopted the model of rigid interlocking asperities as the cause of frictional resistance. (Euler considered Leonardo's experiments of the sliding block on the inclined plane.}

He assumed that the friction force results from gravitational forces, trying to minimize the potential energy of the block. He found the relation between inclination angle and friction coefficient m. We find this relation also by equating the friction force with the accelerating force.

Assuming a velocity-independent friction coefficient, he found, that for the critical angle a the acceleration of the block should be exceedingly small, since gravity is nearly compensated by kinetic friction. This result was against the experimental facts, where sliding started relatively fast. He concluded, that one has to distinguish between static and kinetic friction and that static friction is always larger than kinetic friction. With these assumptions he was able to describe the motion of a block on an inclined plane. Euler was the first who distinguished between static and kinetic friction.

## Sources

"Leonhard Euler." Bio. A&E Television Networks, 2014. Web. 10 Dec. 2014.

http://www.nano-world.org/frictionmodule/content/0200makroreibung/0400historisch/0300euler/?lang=en

Stetson.edu. March 2008. Document. 10 December 2014.