« first day (1017 days earlier)      last day (41 days later) » 

5:34 AM
@JohnRennie, morning.
 
@yuvrajsingh hi :-)
 
Good Morning sir :-) @JohnRennie
 
@user8718165 hi :-)
 
@JohnRennie Sir, winter bash's on :-) I also need hats :-(
 
I recently posted a question, on space. Stack exchange.
@JohnRennie
0
Q: Space and Newton laws

yuvraj singhActually I am a high school student reading about Newton law, like inertia, momentum, and third law. When I start thinking about space, is Newton law are sufficient to describe, events that happened in space. Can we govern everything in the universe for eg. We drive angular velocity, of an plane...

Is it rightly framed, or any error you find in the question ¿
 
5:38 AM
I think you need to make it clear whether you mean Newton's laws of mechanics, or Newton's law of gravity.
Newton's laws of mechanics apply when velocities are low in comparison to the speed of light, and for faster speeds we need to use special relativity.
Newton's law of gravity applies for weak to medium gravitational fields, and for stronger gravitational fields we need general relativity.
 
@JohnRennie ah, OK sir.
I will update my question.
Actually sir if u notice, I have written an event in last.
 
For example do you know about the anomalous precession of Mercury?
Or you might be interested in this question:
105
Q: Could we send a man safely to the Moon in a rocket without knowledge of general relativity?

DargscisyhpI'm wondering if it's possible to send a man to the Moon using equations consistent with Newtonian gravity and without the elaborate tools of Einstein gravity. Are the predictions made by Newtonian gravity sufficiently precise to plan a successful voyage? If not, where would the Newtonian equatio...

 
Through general relativity right sir.
 
Yes
 
@JohnRennie i have read something about it.
If I say anything wrong please correct me OK.
This precession rate had been precisely measured using data collected since the 1600's, and it was later found that Newton's theory of gravity predicts a value that differs from the observed value. That difference, which I am calling the anomalous precession, was estimated to be about 43 arcseconds per century in Einstein's time.

I have heard that general relativity predicts an additional correction that is almost exactly sufficient to account for that 43"/century difference
This was the lines which I remember.
 
5:48 AM
@yuvrajsingh Yes, that's correct.
 
@JohnRennie actually I was reading your answer.
@JohnRennie please go to my question again, they are closing it with a stupid reason.
 
I'm not sure your question is really on topic for the Space Exploration SE. Unless you were specifically asking about how general relativity needed to be taken into account for planning space missions.
It sounds more the sort of question I'd ask here or on the Astronomy SE.
 
@JohnRennie I have some questions, can you. answer please.
Rest I will delete the question.
 
Monday mornings are pretty busy for me. I need to start work in about 20 minutes then I'll be working for hours. But if you have a quick question I'll try and answer it.
 
It might get lengthy, once you finishes the work. Ping me.
 
6:01 AM
OK
 
Yes?
 
OK, is the house Speaker in Britain is queen.
Or king.
 
There is a role called "The Speaker of the House" but that is an appointed role not the King or Queen.
The Speaker of the House of Commons is the chief officer and highest authority of the House of Commons, the lower house and primary chamber of the Parliament of the United Kingdom. The current Speaker, Sir Lindsay Hoyle, was elected Speaker on 4 November 2019, following the resignation of John Bercow. The Speaker presides over the House's debates, determining which members may speak and which amendments are selected for consideration. The Speaker is also responsible for maintaining order during debate, and may punish members who break the rules of the House. Unlike presiding officers of legislatures...
 
@JohnRennie, Hi sir. May I ask a quick doubt from Polarization?
 
6:09 AM
@M.GuruVishnu Yes
 
@JohnRennie, Sir, when a light ray is incident at Brewster's angle, how would you explain that the reflected ray is polarized completely but the refracted ray isn't in an intuitive manner? (I read a question on PSE which wasn't useful to me)
 
I'm not sure there is an intuitive way to explain this.
The reflection and transmission coefficients are calculated by requiring that the electric and magnetic field of the light be continuous across the interface. In principle this is a simple requirement, but in practice it gets very complicated.
 
@JohnRennie By intuitive way, I meant by not using Fresnel equations (which I don't know) sir.
 
You end up with the Fresnel equations and these are pretty complicated.
@M.GuruVishnu that's the problem, I don't think there is an intuitive explanation. Or at least I don't know of one.
 
Ok sir. I'll just accept them as a fact and proceed. Thank you for your time :-)
 
6:33 AM
@JohnRennie morning hi, Alesha here.
Can you answer my quick question.
 
@yuvrajsingh hi. I'm working now I'm afraid. I'm going to be working for several hours. Monday mornings are very busy for me.
 
It is a short one.
I promise it will not take much time. @JohnRennie
 
@yuvrajsingh Go on then :-)
 
Actually, I have difficulty in understanding one easy question, question says a man can, t see distinctly object at distance more than 60cm.the power of the lens will be.
Now my query is. @JohnRennie
There tow cases when men can, t see the object either light rays converge before the retina or light rays converge beyond the retina.
So how do I identify which cases is applying here.
 
The implication is that the man can see things well when they are closer than 60cm but not when they are farther away than 60cm.
 
6:40 AM
Yes.
 
So at infinity the rays are converging before the retina, then as the object gets closer the image distance $v$ increases until it matches the distance to the retina at $u = 60cm$.
 
OK,
So, what about power then
 
Well the power is just $1/f$ isn't it?
So you calculate $f$ from the info you're given and from that calculate the power.
Oh wait. You mean you're being asked the power of the lens needed to correct the man's eyesight?
 
Yes.
 
@yuvrajsingh The total focal length of the lens in the man's eye and the correcting lens needs to be equal to the length of the man's eye, i.e. the distance to the retina. Yes?
That way he gets a perfectly focused image when the object is at infinity.
 
6:49 AM
So 1/f=1/v
That is equal to retina distance.
 
Let's call the retinal distance $\ell$, then the total focal length has to be $\ell$ so the total power has to be $1/\ell$.
 
The power of the lens in the eye is $1/f_{eye}$ and the power of the correcting lens is $1/f_{lens}$, and powers add. So we end up with:
$$ \frac{1}{\ell} = \frac{1}{f_{eye}} + \frac {1}{f_{lens}} $$
And you can calculate $f_{eye}$ from the fact the man can see a clear image at $u = 60cm$.
 
So what I take for v, for the eye lens. @JohnRennie
 
@yuvrajsingh you known that when $u = 60cm$ the image distance $v = \ell$. Yes?
Because at 60cm the man can see the image clearly.
@yuvrajsingh Yes?
 
7:00 AM
OK.
 
So:
$$ \frac{1}{f_{eye}} = \frac{1}{60} + \frac{1}{\ell} $$
And you can use this to substitute for $1/\ell$ in the first equation.
 
But still l is unknown here.
@JohnRennie
Sorry sorry, my mistake. Tha KS sir.
I have wastes your time.
 
:-)
 
 
3 hours later…
10:19 AM
@JohnRennie. Hi.
 
@yuvrajsingh hi :-)
 
Are you free now.
@JohnRennie
 
10:36 AM
@yuvrajsingh I'm doing bits and pieces of work, but I can chat as well :-)
 
 
5 hours later…
3:56 PM
hello sir @JohnRennie Is your lunch finished sir?
 
@user8718165 yes. If you want to ask anything I'm free.
 
And freedom tastes of reality?
 
@skillpatrol reality is over-rated. I avoid it if at all possible.
 
4:15 PM
@JohnRennie, hi.
 
@yuvrajsingh hi
 
Sir, can I ask your typing speed per minute.
 
I'm a really slow typist.
 
I am too.
There are some INSTIUTE which provide typing course.
 
I never learned to touch type, and now I'm getting old my fingers are starting to stiffen up so I'm even slower :-)
 
4:17 PM
Ah,.
 
@yuvrajsingh actually I wish I had learned to touch type. If you have the opportunity to go on a touch typing course I would take it.
 
Actually I am learning it online.
 
Pretty much all the programmers I know who have taken touch typing courses have found it very useful.
3
@yuvrajsingh if the online course is good then go for it
 
Yes.
He is a very good teacher, which genuine method.
 
@user8718165 you found a hat typo! :-)
 
4:19 PM
But he said we have to practice every session 7 times.
 
@yuvrajsingh see how it goes I guess.
 
@JohnRennie Yeah sir.... :-)
 
Actually today lecture he said.
 
If you can do fewer repetitions and still type fast then go for it.
 
To put our figures on second row. Asdf leave gh. For second and fingers.
 
4:21 PM
@user8718165 I suspect your post will be closed because it's not really a physics SE related post. It should probably have been on the mother meta.
 
@JohnRennie problem is that, I am using laptop, so I am not sure whether it really help to increase speed.
 
@yuvrajsingh how are you finding it? Are you finding his advice works?
 
@JohnRennie okay sir...Can I post there?
 
@JohnRennie, yes, his first advice was to type correct, rather increasing speed.
 
@user8718165 yes, if no-one else has posted about it already.
@yuvrajsingh that makes sense I guess.
I don't really know because I'm such a bad typist! :-)
 
4:25 PM
Let see, today I completed 45min, typing first lecture homework.
 
why not relearn now sir?
 
@skillpatrol I don't care about it enough to put the effort in :-)
 
@JohnRennie can you make me room owner.
 
@yuvrajsingh have you found it made your typing better?
@yuvrajsingh yes, let me see if I can figure out how to do that ...
 
4:27 PM
Actually today it was first day., so actually I missed the process but yes it works.
 
@JohnRennie sir I also want a hat :(
 
congrats @yuvrajsingh^
 
@user8718165 You have to work for the hats! :-)
 
So gentle, the room is discussion for pure physics. It is better to discuss non physics related talk on Chitt chat and stuff
 
I can see this going horribly wrong :-)
 
@JohnRennie thanks for the Christmas Gift sir :-)
 
@yuvrajsingh speed typing comes much, much later... after a lot of practicing the accurate typing style
11 mins ago, by yuvraj singh
@JohnRennie, yes, his first advice was to type correct, rather increasing speed.
 
@sammygerbil Hello :-)
 
4:52 PM
@JohnRennie sir, when your avatar is small (one-line messages) you look like a pirate XD
 
@user8718165 :-)
 
 
2 hours later…
7:08 PM
Hello
I am trying to develop a 2d physics simulator, like gravity and other mechanics stuff. If anyone can guide me whether to write my own engine or use already available engine like box2d
If anyone has such knowledge then please help me!
 

« first day (1017 days earlier)      last day (41 days later) »