10 Examples of Physics From Everyday Life

Not every student will grow up and study physics on a deeper level, but physics extends well into our daily life, describing the motion, forces and energy of ordinary experience. Therefore, it should be possible to illustrate to anyone the physics of everyday life, with examples of course.

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Image formation

Have you noticed that when standing inside a room at night, you can often see your reflection in a pane of glass? In similar way, because there is much less light coming from the bottom of a lake, the surface of the lake will act like a mirror.

But an image can also be formed by refraction. A fish seen in the water will usually appear to be at a different depth than it actually is, due to the refraction of light rays as they travel from the water into the air.

Lastly, there exist phenomena which appear due to combination of reflection and refraction. For example, a rainbow is seen when light passes through water droplets hanging in the atmosphere. The light bends, or refracts, as it enters the droplet, and then reflects off the inside of the raindrop.

Washing machine

The dryer of washing machine is a rapidly rotating container that applies centrifugal force to its contents. The centrifugal force acts in a direction away from the centre and hence can be used to throw the water molecules on the clothes radially outwards during the spin cycle of the washing machine.


Static electricity

When two objects that are not good electrical conductors are rubbed together, electrons from one of the objects rub off onto the other.

The more rubbing between two objects, the more static electricity build up and the larger the electrical charge.


Road safety

When brakes are applied to a moving car, the car and lower portions of the passengers attached to the car come to immediate stop, but their upper portions fall forwards, because of inertia. This is why seat belts as well as air bags are installed in the car.

Roller coaster

The first hill of the ride is always the highest one so that the car collects enough energy to go through all the elevations. As the car goes down, its potential energy decreases but kinetic energy increases. If added together at any part of the ride, the kinetic and potential energies of the car will equal the potential energy that the car had on the first hill.


Spinning

When the figure skater draws her arms and a leg inward, she reduces her moment of inertia thus rotating at a faster angular speed. This is due to conservation of angular momentum.

Handle of the door

If you apply force close to the hinge of the door, the door will not open as it will not be able to rotate about the hinge. But, when you apply the same force farther away from the hinge, the torque will be larger. Hence, the door opens easily with less effort.

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Falling down

Suppose you are climbing a tree, and suddenly you slip and fall down from the tree. Then, you may break a bone or two. But if same thing happens to a little ant, that is, if it falls down from height, it does not get hurt. Why is it so?

From ant’s point of view, the atmosphere is thick and viscous and its experience of falling from a height is similar to ours when we fall through water to the bottom of the pool. The air underneath the falling ant becomes like a large cushion of safety.


Roundness

Nobel prize winning physicist Richard Feynman explains why little drops of water are round in the following video.



Sound game

When a water bottle fills up, the air column or amount of air inside the bottle decreases. As a result, the pitch (or shrillness) of the sound will increase, as it is inversely proportional to the length of vibrating air column. Therefore, you can tell exactly when the bottle is full without even looking.

Summing up

It is hard to imagine of life without physics. Even though one may not be equipped with the kind of mathematics required to fully understand these physical phenomena, one can surely appreciate the fact that they are there. Lots of other examples are available and you just need the eye to recognize them.

Dirac, a fusion of genius and madness, according to Einstein

Paul Dirac, one of the most famous scientists of the 20th century, was a very quiet man. So much so, that his colleagues at Cambridge jokingly defined a unit of speech called "dirac", which meant one word per hour!

But whenever he did speak, Dirac used to extend his abstract thinking to interpret the world literally. This inevitably led him to being an anecdote generator throughout his life and many stories about him abound.

Why do you dance?

In 1929, Dirac and Heisenberg were on board a ship to Japan for attending annual science conference. Werner Heisenberg who happened to be quite a ladies man, used to dance with the young girls on the ship before dinners, while Dirac used to sit watching.

One such evening, Dirac asked, "Heisenberg, why do you dance?"

"When there are nice girls, dancing with them is a pleasure," Heisenberg replied.

Dirac pondered this notion for a while, then blurted out: "But, how do you know beforehand that the girls are nice?"

Heisenberg burst out with laughter.

Physics versus poetry

Dirac and Oppenheimer spent some time together in Göttingen. The two young physicists from different parts of the world had become good friends. In one of these days, Dirac noticed that Oppenheimer wrote poetry.

Dirac asserted, "Robert, I do not understand how a man can work on the frontiers of physics and write poetry at the same time."

"Why not?" Oppenheimer asked.

"In physics, you want to tell something that nobody knew before, in words which everyone can understand. In poetry, however, you go on to describe something that everybody knows about, in incomprehensible ways."

Oppenheimer was left too confused to respond to that.

Dirac went on to say, "The two are incompatible!"

His comments would strike people as odd at first but they would quickly realize that Dirac made perfect logical sense.

Finish this sentence

Once, Dirac and Bohr were seated in the same room. Niels Bohr, known for being a perfectionist, was writing a scientific paper while mumbling at the same time as was his habit.

After some time, Bohr became really frustrated and stopped. He complained, “I do not know how to finish this damn sentence!”

Dirac retorted, "I was taught at school, never to start a sentence without knowing the end of it."

Dirac said something so profound, with such a straight face, that Bohr went on to comment, "Dirac was the strangest man who ever visited my institute!"

I have an equation

American physicist, Richard Feynman, born in 1918, grew up idolizing Dirac. About 40 years later, they met in Poland at a conference. Richard Feynman, by then a theoretical physicist himself, was building upon Dirac's great work.

Feynman, the chatty one, spoke at length, as he wanted to describe new ideas to his hero. Dirac, perhaps intimidated by Feynman's over-enthusiasm, remained quiet all along.

Feynman started to see that it was extremely difficult to get anything out of Dirac. But then, after a long silence, Dirac says, "I have an equation. Do you have one too?"

Dirac also went on to explain as to why he spoke so little, “There are always more people willing to speak than there are to listen.”


That wasn't a question

In 1932, Dirac was appointed the Lucasian Professor of Mathematics at the University of Cambridge. During one lecture in class, a student raised his hand and said, "I don't understand the equation on the top-right-hand corner of the blackboard."

Dirac simply nodded his head in agreement and continued unabated. When asked again, he expressed puzzlement because he thought the student had simply uttered a fact and not asked a question.


Summing up

Paul Dirac knew not when to say what. He remained merry in his own company but suffered agonies if forced into any kind of socializing or small talk.

His colleagues  in Cambridge described him as a “lean, meek, shy young fellow who goes slyly along the streets, walks quite close to the walls, like a thief, and is not at all healthy.”


Albert Einstein once commented on Dirac: "I have a lot of trouble with Dirac. This balancing on the dizzying path between genius and madness is awful!"

Dirac quantised the gravitational field, formulated the most logically perfect presentation of quantum mechanics and predicted the existence of anti-matter. At the same time, he was also equally famous for his strange, unapologetic behavior.

Nikola Tesla, a college dropout who changed the world

On 10th of July in 1856, Nikola Tesla was born at midnight during a lightning storm. The midwife thought the violent storm was bad omen, "This will be a child of darkness", she declared mindlessly."No, replied Tesla's mother, "he will be a child of light".

His father, Milutin Tesla, was orthodox christian priest while his mother, Đuka, was hard working housewife. They recognized very early that their son was unlike other children. Young Tesla was creative, curious and blessed with photographic memory.

Milutin, a devout man, wanted his son to become priest like himself but Đuka encouraged Nikola to study science instead. Even though she had never received formal education, Đuka had the talent for making mechanical appliances at home.

Nikola Tesla's parents

By the age of 16, Nikola was able to perform integral calculus in his head which prompted his teachers to believe that he was cheating. Tesla credited his eidetic memory and creative abilities to his mother's genetics and influence.

He finished four-year high school term in three years graduating in 1873. During those times, high school graduates were forced to join the military but Tesla ran away and remained hidden for over a year wearing hunter's garb to escape conscription.

Tesla returned in 1875. Then, he enrolled for engineering degree at Graz University of Technology in Austria.

In first year, he never missed a lecture, earned the highest grades and even received letter of commendation from the dean to his father, which stated, "Your son is a star of first rank."

But 20-year old Nikola was mortified when his father made light of those hard won honors. In second year, Tesla came into conflict with his professor when he suggested that commutators would be unnecessary in the Gramme Dynamo.

Tesla lost the scholarship money as he became addicted to gambling. In third year, he did not even sit for the examination. He severed all relations with family to hide the fact that he had dropped out. At age 22, without contacting anyone, Nikola moved to Slovenia in search of work.

His family thought that he had committed suicide but one year later,

In March of 1879, Milutin learned that his son was seen in Maribor, the second-largest city of Slovenia. He went to Maribor to beg his son to return home. Tesla refused.

street where Tesla lived in Maribor

Milutin was despaired. In April of 1879, he passed away aged 60. After hearing the news, Nikola returned home but too late though.

A sorrowful Nikola recalled, "My father wanted me to enter priesthood but in one of the sinking spells due to Cholera, which was thought to be the last, he rushed into my room. I still see his pallid face as he tried to cheer me up..

"Perhaps," I said, "I may get well if you will let me study engineering."

"You will go to the best technical institution in the world," he solemnly replied.

Nikola was lost and depressed especially after death of his father. He stayed home for few months. Then, he started teaching at his old primary school. He taught there until January 1880.


Next, he went to Prague and attended lectures in philosophy for a year. In 1881, Nikola moved again, this time to Budapest to work for Budapest Telephone Exchange. He was 25 years old.

In 1882, he was employed as electrician by Continental Edison Company in Paris to install incandescent lighting. The management took notice of his advanced knowledge and soon he was promoted.

"In 1884, I was brought in intimate contact with Edison. His mind was dominated by one idea, to leave no stone unturned and to exhaust every possibility. We experimented for days and nights, holidays not excepted."

During this time, Edison made an outstanding offer. In exchange for redesigning generators, Tesla was promised a hefty cash prize.

But he was taken advantage of as it turned out to be a practical joke. Therefore, in January 1885, a furious Tesla left note for Edison which read, "Goodbye to the Edison Machine Works."

For a brief while, Nikola Tesla remained jobless in America.

Then, with help from interested investors, Tesla founded a company in his own name, Tesla Electric Light & Manufacturing (1885). He worked for the rest of the year acquiring patents for improved design of DC generator which had gained recognition in the press.


But Nikola was not business-ready yet.

In 1886, the investors obtained control of the patents, renamed the company to Union County Electric Light & Manufacturing and left Tesla penniless in the process.

"My life seemed to me like mockery."

Yet, Tesla did not give up as he set about to create another company, this time with more caution, in 1887. He invented commutator-less induction motor in the same year. This innovative machine which ran on alternating current was patented by Tesla in May of 1888.

Soon, $15,000-a-year royalty deal was made for the new type of motor with Westinghouse Electric Company.

Induction motor by Tesla

But two years after signing the Tesla contract, George Westinghouse was in deep financial trouble. Also, at this time, Edison came out with all guns blazing against the alternating current movement, saying, "It is too dangerous. Direct current is safe."



In 1891, Westinghouse explained his situation to Nikola Tesla and Tesla agreed to release Westinghouse Company from the royalty payment.

Six years later, when all troubles sorted, direct current defeated, Westinghouse purchased Tesla's 1888 motor patent for a lump-sum of $216,000. The money made Tesla independently wealthy and gave him the time and funds to pursue his own interests.

Nikola Tesla went on to obtain around 300 patents in over 25 countries for his inventions. Tesla coil, remote control, induction motor, neon lamp, wireless telegraphy to name a few.

on the cover (1931)

Tesla died on 7 January in 1943 at the age of 86. He never married, did not have any children and devoted his life totally to the pursuit of knowledge and innovation.

"To me[Nikola Tesla], the universe is simply a great machine which never came into being and never will end and what we call 'soul' or 'spirit,' is nothing more than the sum of the functionings of the body. When this functioning ceases, the 'soul' or the 'spirit' ceases likewise".