Guitar - Easiest song to Play - Happy Birthday Song

Easiest Song to Play

Skills needed: Three chords G, C, D. Able to transition quickly. No strum skill needed. No timing skill needed.

I got this information from youtube "10 Easy Songs 3 Easy Chords G C D" from Lee John Blackmore ( at time 11:29). Click here to directly reach to that song:

 https://youtu.be/zi6CRi0SXLM?si=VCA6gXjOLhAReopb&t=11m29s

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Poem - A Leaf Treader - that motivated me in corporate life

 You may all have heard the famous poems of Robert Frost - "Stopping by Woods on a Snowy Evening" and "The Road Not Taken". While these are great inspiration for young minds. What about the drudgery of corporate life. In corporate life you may enjoy the technical challenges and find it greatly rewarding, but what about people challenges that can makes the environment unbearable. 

Here is that poem that motivated me in corporate life and will inspire you:

A Leaf-Treader

I have been treading on leaves all day until I am autumn-tired.
God knows all the color and form of leaves I have trodden on and mired.
Perhaps I have put forth too much strength and been too fierce from fear.
I have safely trodden underfoot the leaves of another year.

All summer long they were overhead, more lifted up than I.
To come to their final place in earth they had to pass me by.
All summer long I thought I heard them threatening under their breath.
And when they came it seemed with a will to carry me with them to death.

They spoke to the fugitive in my heart as if it were leaf to leaf.
They tapped at my eyelids and touched my lips with an invitation to grief.
But it was no reason I had to go because they had to go.
Now up, my knee, to keep on top of another year of snow.

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Does particle moving in a straight line have Angular Momentum?

The answer to the title question is simple, ask yourself the question: Does the moving particle has the ability to create a rotation motion? If yes, then it has the angular momentum, otherwise: no. It all depends on the pivot you choose.  Let me show you by a gedankan experiment (The phrase Gedankan experiment, which means Thought Experiment, became popular after Einstein used in explaining his Relativity theory). 

Consider the figure below:

In the gedankan experiment, a bullet is approaching a wooden-block. The wooden-block is initially at rest that is free to rotate around a pivot. The bullet hits the wooden-block gets embedded into the log and the combined wooden log with embedded bullet starts rotating clockwise (CW)

Since it is rotating, it has angular momentum. Angular momentum of isolated system is always conserved. Where did this angular momentem come from? Initially there was no angular momentum of the block as it was at rest. So it could have only come from the moving bullet. 

But if the bullet was going to hit the pivot as shown in figure below:

Here the block would not rotate and therefore, in this situation, the bullet has no angular momentum. It all depends on the position of pivot.

Now, let me give you the answer. The magnitue of angular momentum of bullet is (also see the figure below): 

$$|\vec{L}| = mvb $$

where \( m \) is the mass of the bullet, \( v \)  is the initial velocity of the bullet, and \( b \) is the distance of the closest approach of the bullet to the pivot. It is also called as Impact Parameter.   Clearly, you can see that in the second case discussed above when the bullet is hitting on pivot the impact parameter is zero, and therefore the angular momentum is zero in second case.

This phrase became popular aftter Ernest Rutherford used when describing his model of the atom.

When dealing with non contact forces such as gravitational forces, or electromagnetic forces. The impact parameter should be considered as if there were no such forces, i.e., the bullet travelling in straight line and the distance of closest approach to pivot is the impact parameter.   

I will leave to reader to calculate the angular momentum,  based on mathematical formula  

$$\vec{L} = \vec{r} \times \vec{p} \quad or  \quad L = r_{\perp} \times p \quad or \quad  L = r \times p_{\perp} \quad =mvb \quad$$  

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An amazing circuit that can produde 1000s of volts from a simple battery

I wished I was taught in High school or even college. Sigh! I found out when I was tutoring a student from a premier European university. 

It is used in ignition coil to generate 1000s of voltage to produce the spark that makes controlled explosion in the car/motorcycle/scooter  (remember spark plug)

The Amazing Simple Circuit

This is that simple circuit:

The Problem:

Let me state the problem: The circuit initially has the switched closed for quite long time and steady current flows. (the inductor is fully loaded with magnetic field). When this switch is open, what is the voltage across AB at that instant of time?

Here is the answer:

In the initial condition, at steady state, when the switch is closed. It acts like simple DC circuit with battery and two resistances. Inductor acts like a simple wire (because the current is not changing) with zero resistance . From simple circuit analysis, the currents are given as follows (Note A is positive):  

$$  I_1 = \frac{V_0}{R_1},  I_2 = \frac{V_0}{R_2}$$

Now, when the switch is open, some thing amazing happens at that very instant. The inductance opposes the action (Lenz's Law) and responds by maintaining the same current in inductance, which is  \( I_2 \).

But the circuit is different now (also note the A has become negative, earlier it was positve. In short, A and B has changed the polarity) and shown below:

The current \( I_2 \) now flows across \( R_1 \) and \( R_2 \). The voltage across AB is same as voltage across \( R_1 \), which is \( I_2 \times R_1 \), the voltage across AB then is:

$$  V_{AB}= I_2 \times R_2 = \frac{V_0}{R_2} \times R_1 $$

What is amazing is the voltage does not depend on the value of inductance!! Such a simple circuit. Don't you think it deserves to be taught in High school or Junior college? The fact that this beautiful question is taughter in European university, explain why Europe leads in many area of science!

Then what the purpose of having inductance with large value? Well, after the circuit is open, the current \(   I_2  \) is generated by inductance coil. And if inductance is large, it can maintain the current for a longer time. From the point of energy, large inductance mean, the coil contains more magnetic field. The magnetic field takes more time to exhaust itself.

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Test friend's character by giving money

When a friend asks for a modest amount of money, my advice is to give it gladly. It’s a test of their character. I tell my children: you spend thousands on the college education to learn skills, but by giving $50–$100, you can learn a friend’s true character. That’s quite a bargain!

Never expect to get the money back, so only lend what you can part with without regret.

You’ll find that very few people return the money. If someone does, they’re a worthy friend, one worth keeping close!

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Corporate world - Cheering on your own misery!

It may very well have happened to you 😀, when attending the company's meeting. Your manager getting praised for boosting efficiency and profits. And you cheering for "our" achievement.

But it could very well be, not due to company getting new projects. But squeezing the teams by firing your colleagues and make you work harder. It is really his achievement  that will get him a higher bonus and you will get more work! Yet you cheered for it.

Don't worry, it happens to all. It takes a while to wisen up 😀

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z-library link - The latest one that is working!

Z-library latest link is: https://z-library.sk/ last checked on 24-July-2025. 

The link keep changing as it is illegal in many countries: USA, France, Germany, India, UK and Australia to name a few. Please use at your own risk. 

It aligns with philosophy "Information wants to be free" attributed to Stewart Brand (1984). It appears almost any book is available there for free. Small donation is suggested if you like to have large download in a day.

The purpose of this post is to provide you with correct link and avoid scam/phishing links. 

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