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6:59 AM
@JohnRennie hi
 
@yuvrajsingh hi. I need to work now for a bit. Is it a quick question?
 
Yeh I have some doubt regarding force.
 
@yuvrajsingh yes?
 
I have doubt the generally we have four kind of forces in nature, and nuclear force is one among them.
forces has one thing that is they. change momentum
@JohnRennie
Or they change shape too. Sometimes OK.
Are you there.
 
7:16 AM
@yuvrajsingh hi
 
You need to be a bit cautious about the word force.
 
Why.
 
Really we have four interactions, and of those four the EM and gravity interactions produce the classic EM force and gravitational force at low energies/large distances.
But the weak and strong interactions have no equivalent classical force.
So to talk about the weak and strong force is really a misnomer, though all physicists know what this really means.
 
Weak are you saying about the nuclear forces.
@JohnRennie
 
7:22 AM
@yuvrajsingh yes, the weak and strong nuclear forces.
 
But they show their significance in beta decay and other nuclear process. @JohnRennie
Is the definition of force is not work for them.
 
@yuvrajsingh the point is that they aren't really forces in the sense that we can write then as $F(r)$ for some distance $r$.
When we talk about weak and string interactions what we are really doing is calculating scattering probabilities.
 
, so what can I call that happen inside the nucleus.
 
And that includes the probability that new particles will be created during the scattering e.g. like new particles are created at the LHC.
 
But sir, Einstein energy mass relation still describe their existence.
@JohnRennie
 
7:28 AM
Energy is always conserved so if $M$ is the total rest mass of all the particles and $T$ is the total kinetic energy of all the particles then $Mc^2+T$ is constant.
But in scattering KE can be converted to mass and mass can be converted to KE.
So neither $M$ nor $T$ are constant on their own. Only the total energy $Mc^2 + T$ is constant.
I need to work now I'm afraid. I'll be about half an hour.
 
We solve momentum equation for this small particle, then theor should be talk about force.
@JohnRennie
 
8:07 AM
@yuvrajsingh hi, I'm back.
Momentum is conserved in the scattering, but that doesn't mean the scattering process can simply be interpreted as a force. For example the total rest mass of the particles present can change due to the creation of new particles.
That messes up the simple Newtonian equation $F=ma$ because $m$ is no longer constant.
 
8:31 AM
Thanks sir I got my all point s sir I have one more question. @JohnRennie
 
Yes?
 
@JohnRennie can you answer the edit part. astronomy.stackexchange.com/questions/33808/…
 
You mean how do we define an origin?
 
Yes, with my concern I mention.
@JohnRennie
 
I think we need to distinguish between the mathematical ideal of defining a coordinate system and the physical reality of a physicist floating in space trying to define a coordinate system.
 
8:40 AM
@JohnRennie can you write your answer. There.
 
A completely empty universe is static i.e. unchanging in time. So it makes no difference where we place the origin. Mathematically we can arbitrarily choose a point as the origin and that's a perfectly fine thing to do. The universe is a 4D manifold and we can choose any random 4D poitn and say "that's our origin".
 
Please sir, @JohnRennie
 
@yuvrajsingh I can post an answer, but writing an answer takes a lot longer than just making a few comments in the chart because the answer has to be clear and well written. So I can't do it right now.
 
I am not saying you post it right now, you can post it any time you want, so that other user who have similar problem can understand better.
@JohnRennie
 
 
2 hours later…
10:41 AM
@JohnRennie are you free now.
 
Is it a quick one? I have some work to do.
 
Yes it is short. @JohnRennie
Are you OK with metallurgy.
 
@yuvrajsingh Hmm, it depends what you want to ask. I have done some metallurgy ...
 
Sir do you remember, purification of znso4
@JohnRennie
 
Purification of zinc sulphate?
How is that being done? Recrystallisation?
 
10:51 AM
Yes.
@JohnRennie
Are you there.
 
What did you want to ask?
I don't think I've ever recrystallised zinc sulphate but I doubt it's complicated.
 
I have three process mention can you explain them
In the process for electrolysis for zinc, three things must be done:

Leaching the ZnO
Purifying the ZnSO4 by means of cementation
Performing the electrolysis
@JohnRennie
 
I don't think I can help. The best I could do is Google it.
 

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