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# Monthly Archives: May 2016

## The physics behind railway ticket booking

Posted as received via WhatsApp
Do you Know why  IRCTC does not allow you to choose seats? Would you believe that the technical reason behind this is PHYSICS.

Booking a seat in a train is far more different than booking a seat in a theatre.

Theatre is a hall, whereas train is a moving object. So safety concern is very high in trains.

Indian railways ticket booking software is designed in such a way that it will book tickets in a manner that will distribute the load evenly in a train.

Let me take an example to make things  more clear : Imagine there are sleeper class coaches in a train numbered S1, S2 S3… S10, and in every coach there are 72 seats.

So when some one first books a ticket, software will assign a seat in the middle coach like S5, middle seat numbered between 30-40, and preferably lower berths (Railways first fills the lower berths than upper one so as to achieve low centre of gravity.)

And the software books seats in such a way that all coaches have uniform passenger distribution and seats are filled starting from the middle seats (36) to seats near the gates i.e 1-2 or 71-72 in order from lower berth to upper.

Railways just want to ensure a proper balance that each coach should have for equal load distribution.

That is why when you book a ticket at the last, you are always allotted an upper berth and a seat numbered around 2-3 or 70, except when you are not taking a seat of someone who has cancelled his/her seat.

What if the railways book tickets randomly ? A train is a moving object which moves around at a speed of around 60 Kms/hr on rails.
So there are a lot of forces and mechanics acting on the train.

Just imagine if S1, S2, S3 are completely full and S5, S6 are completely empty and others are partially  full. When the train takes a turn, some coaches face maximum centrifugal force and some minimum, and this creates a high chance of derailment of the train.

This is a very technical aspect, and when brakes are applied there will be different braking forces acting at each of the coaches because of the huge differences in weight of coach, so stability of train becomes an issue again.

this is a good information worth sharing, as often passengers blame the Railways citing inconvenient seats/ berths allotted to them.

## CBSE class X results 2016

CBSE will announce the class X results on Saturday 28 May 2016.
The results can be seen from http://cbseresults.nic.in

## Question from Einstein’s Theory of relativity

From: venky
Subject: einstein’s theory of relativity

Message Body:
when two electrons leave a radioactive sample in opposite directions, each having a speed 0.67c
with respect to the sample, the speed of one electron relative to the other is
l.34c according to classical physics. What is the relativistic result?
We may regard one electron as the S-frame, the sample as the S’-frame,
and the other electron as the obje(‘t whose speed in the S-frame we seek . Then
u ‘ = 0.67c
v = 0.67c
and
u=
u ‘ + v = (0.67 + 0.67)c = 1.34 c = 0.92c.
1 + u ‘ v/c’2 1 + (0.67)2 1.45
The speed of one electron relative to the other is less than c.
but what if  one takes the other electron as the other frame(S’) ,in that case v=1.34c ,explain?

## Question from quantum field theory

From: Krish <krish.tibrewala@gmail.com>
Subject: Quantum field theory

Message Body:
This question relates to the gauge theories behind the strong, weak and electromagnetic forces. A beautiful intertwining of theoretical physics and pure mathematics is when group theory is used to described these forces. For example, the Standard Model of particle physics is perfectly described by: SU(3) x SU(2) x U(1)…..I have enough knowledge in group theory to understand special groups (or at least, understand their conditions) and the unitary group.

However, what I do not understand is how the aforementioned groups even represent the fundamental forces, how they even come into play!

If I had to sum it up, this is my question:

“How is the symmetry SU(2) x U(1) broken? What does it mean for the maths….how is the mathematics adjusted….What does a broken symmetry really MEAN mathematically? How are SU(2), U(1) etc even INVOLVED physically anyways?? Like, how do they represent The weak and electromagnetic forces?”

Thank you very much for your time and help

## The dimples of a golf ball

How exactly do the dimples of a golf ball affect the way it flies? What are the different materials golf balls are made of and how do they affect the balls flight/takeoff?

The basic role of the dimples is to mdecrease drag and thus enabling the ball to cover greater distances.

Golf is normally played at open areas with calm surroundings. The flow of air islly the drag is less but when the ball iinitially the drag is less but when the ball is tring to separate the laminae of air, the drag increases.

But with a large nuber of dimples, the flow is mase turbulent and drag is reduced thereby enabling the ball to travel greater distances.

## Why is gravitational force less powerful than coulomb force?

Why is gravitational force less powerful than coulomb force?
I know that the theoretical reason is the value of G=6.67*10^-11 ….but what is the practical theory be

hind it and how did coulomb stumble upon such a cryptic formula?

## Why is the mass of proton less than the mass of neutron?

Why is the mass of proton less than the mass of neutron?

The standard values of masses of proton, neutron and electron are as given below.

Particle Charge Mass (g)
Proton +1 1.6727 x 1024 g
Neutron 0 1.6750 x 1024 g
Electron -1 9.110 x 1028 g

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