Chapter 4- The Mechanical World

Its been sometime since we talked about sound and although I want to learn more, the old man says, ” There’s much time left. Don’t be in such a hurry. Absorb slowly and smoothly what you have learnt till now and we can continue afterwards when the time comes.“ As a result, I have been sitting since and getting bored till that moment came.
A man stood up from his seat and was arranging his bags because his station was about to come and then, suddenly the train took a sharp turn to the right and the man fell down only to be saved by his own seat. Although falling down is normal to everyone but to me, it was another result of a physical phenomena since I have learnt that everything around us happens due to the consequences of the laws of nature and inspite of the risk of sounding lame, I asked the old man, “ Why did the man fell down when the train took the turn?“ The old man was pretty surprised and replied, “ I am pretty surprised to see this quality of yours which most people don’t have.“
“ What ? “I asked in confusion and surprise.
“ Its asking questions no matter what it is. Its important to ask questions no matter how bad it is because even the scientists couldn’t do anything if there were no questions to solve. “
“ Was my question a bad one ? “
“ No, on the contrary, its an extremely good one and the roots of this question lays the foundation of mechanics “
“ You mean people who repair cars ? ”
“No, that’s a mechanic and mechanics is the study of motion of bodies “, he replied with a smile
“So, the man fell down because of the movement of train. Right ? “
“Yes, its because of the inertia of direction “
“Now what’s that ? “
“ Well, the tendency of a body to stay in the state of rest or of motion is called inertia “
“ Ohhhh! But how did that’s related to the train?“
“ Well, the train was moving and the man was ok until the train took the turn because the lower part of the man’s body was connected to the train but the upper body was away from the surface of the train so when the train took the turn, the lower part changed its direction with that of the train but the upper part didn’t, so due to this imbalance, he fell down “
“Wow, I didn’t even know that falling down could be so complicated “
“ So it means that inertia is not only dependent on the state of motion or rest but also the direction “


“ Ok, I think I am getting it “
“Speaking of inertia, you don’t know about Newton’s laws do you ? “
“To be honest, No “
“ Then lets start with Mechanics “he exclaimed joyfully.
He started speaking with same enthusiasm when he taught me about sound, “ There are three laws of motion as stated by Newton and you have already learnt the first law “
“No I haven’t “
“Yes you did “
“When ? “
“ Newton’s 1st law states that a body tends to be at rest or at uniform motion unless an external force acts on it. “
“ Wait! Is that inertia ? “
“Yes, and that’s why this law is also known as the law of inertia. It’s the reason that when you keep your cell phone in a particular place, you find it at that particular place tomorrow otherwise things could have started jumping off or could have moved randomly “
“Haaahaa, that was funny” I laughed but then I questioned, “What about a car moving constantly and then coming to rest without pushing the accelerator ? “
“That is the work of friction”
“Wait, weren’t we talking about Newton?”
“Mechanics is a huge topic. In fact, it scales from the tiniest particles like electrons to large astronomical objects”
“Wow, Newton could explain all these things with just three laws?!!”
“Well, not exactly”
“So there’s a 4th law?!”
“No, particles like electrons and protons are subjected to the field of quantum mechanics”
“The name sounds so cool!!!!”
“That’s what most people say when they hear it first time”
“Whoever named it must be a man of culture.”
The old man left a heavy sigh.
“Let us get back to friction and besides, I don’t think that I can teach you quantum mechanics.”
“Come on! I understand sound, I’m sure that I’ll understand quantum mechanics. Also, isn’t it good if we start from smaller to bigger mechanics?”
“I can’t teach you quantum mechanics because I simply don’t understand it and you can’t understand it even if you learn from the best teacher in the world.”
I felt the words to be a bit harsh. Well, I can’t say anything to the old man or he might stop teaching. His words just killed my curiosity about the topic.
The old man continued,”No one in this world understands quantum mechanics!”
I felt intrigued by the statement and asked him, “But aren’t there any people who are studying about quantum mechanics?”
“We have made quite a progress, and yet, we have to go much much further. It is one of the most accurate theories out there but we still can’t quite understand it.”
“So, people are just discovering things randomly without knowing anything?”
“No, we know many things about quantum mechanics but we can’t understand it because we don’t observe an electron moving around in every day life. We can’t visualise it so we can’t understand it. A physicist’s greatest power is imagination which he can’t apply to quantum mechanics.”
I regained my curiosity and it has increased ten times.
The old man continued,”Feynman once said, ‘I can safely say that no one understands quantum mechanics’”
“Feynman said that?!”
“Yes, he did”
“Ok, then let’s get back to friction.”
The old man smiles a bit at me and then he asks,”What was your question again?”
“Why does a car stops moving eventually after sometime when no one’s pushing the accelerator?”
“Now, this is friction. You can say that it is a force which acts opposite to the motion of a body. When you spill water on to a surface, there is a chance that you might slip and fall down. This water reduces the friction on the surface. Such substances which reduce friction are called lubricating agents.”
“So that means friction lets us stand on the surface?”
“Yes! If it weren’t for friction, you wouldn’t have been able to stand and walk properly. Just imagine someone jumping from plane for parachuting, he would experience a tremendous resistance from air. This is also friction.”
“Do raindrops experience friction too?”
“Yes, they do. However, you always something which opposes you for friction to work. In case of a car, it is the road and for the parachute man, it is the air. All of them made up of small particles which oppose the motion.”
“You said that we won’t discuss quantum mechanics?”
“We can discuss friction, quantum mechanics has much more in it.”
“Ok then, continue”
“Now, imagine an astronaut travelling in outer space. If you remember correctly, I have already told you that astronauts cannot listen to the sound of the rocket because of no material medium.”
“Yes, I remember.”
“Since, we also need that friction, we can say that outer space has no friction!”
“Of course, it is vacuum and astronauts move freely in outer space if they somehow get out of their rocket.”
“So, inside the rocket they can move freely?”
“They have gravity inside the rocket which helps them move freely.”
“Ooooh, Gravity!”
“Newtonian Gravity is also included in classical mechanics but we will discuss it later.”
“Newton discovered gravity too?”
“Yes, that’s why he is one of the greatest physicist of all time. If Newton didn’t discover his laws and gravity and everything written in his book, ‘Principia Mathematica’, we physicists couldn’t have done anything!”
I was getting inclined towards a new idol after Feynman, then I asked a question, “What do you mean by ‘Newtonian Gravity’?”
“The theory of gravitation given by Newton.”
“So there’s more of it?!!”
“Yes, there is, but Newton’s laws are the very foundation of physics. You need to understand the core first. You have to feel it’s signifance. You have to connect it to the world. Only then you can proceed to something else.”
I answered in low tone, “I asked too many off the topic questions, didn’t I ?”
“You did, but I would have been disappointed if you didn’t.”
“That’s nature for you. You get a question. While solving it you get 5 more questions and more questions while solving those questions and the process continues.”
I just get more intrigued whenever I listen to him and his way of discussing physics.
“Physics is not only a subject, it is the whole world, the universe. Each and everything in this world exists because of physics and it’s laws. Each and every action is dictated by it. It’s a race against time for the human kind to discover reality and answer the unanswered questions. We are creatures driven by curiosity and this curiosity makes us leave everything behind, friends, family, society, politics, economics and everything to try understanding the world. Physics breaks barriers. It breaks caste, race, nationality, clothes, gender, economy and other barriers. It is much much more bigger than you and me. Science is universal. We live, we die but laws of physics last for eternity. I don’t know if I am a good physicist or not but physics has taught me one thing, every question must have a definable answer.”
I was really getting goosebumps.
The old man continued in a lighter tone, “I guess I went a bit off topic too. But I think it’s important to understand the core of the subject, the nature of physics. I think it’s better if we continue afterwards”
I went a little quiet and just said, “Hmmm”.

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