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1. ### Newton's shell theorem (r=R)

@PeroK ,@vanhees71, it seems this is the case of jump discontinuity And still our solution manages to give average value, how cool is this?
2. ### Newton's shell theorem (r=R)

Wow insight is good and satisfying, is their a mathematical theory behind this?, Some kind of theorem regarding integration ambiguity of this kind?

4. ### Newton's shell theorem (r=R)

First i tried proving Newton shell theorem directly for r=R and solved the integral as above but still got the wrong solution. Here i tried using general case: Here r' is the distance of a small ring from the point particle of mass m So my doubt is when we take r=R and then evaluate this...
5. ### I What does Noether's theorem actually say?

Thank you everyone, her theorem really inspired me, really remarkable, i am a big fan of feynman and from now emmy noether is one of a kind, i think i have to make "list of favourites".:smile:
6. ### I What does Noether's theorem actually say?

So what i undrstood is that yes her theorem can prove if there is a symmetry of such kind then there will be a conservation of particular kind, since maths is so complex i could understand this much only.
7. ### I What does Noether's theorem actually say?

How do we know that such a such type of symmetry will give you such a such type of conservation law Can we simillarly prove that if there is translation symmetry then momentum is conserved and if there is rotational symmetry then angular momentum is conserved.
8. ### I What does Noether's theorem actually say?

I don't know much about classical physics(such as lagrangian function), but as i was reading conservation of energy, i came to this theorem and it tells that if a system is symmetrical in certain transformations(such as translation, rotation etc) then it will have a corresponding law of...
9. ### B What are antiparticles and what do they do?

What are antiparticles and what do they do? How do we know that they do exist? Could you explain these in layman's term,because I don't know much about quantum mechanics.
10. ### Problem with the Definition of work

Sir why i am not able to make a private conversation with you on physics forum
11. ### Problem with the Definition of work

Could you explain it with a physics example(not mathematically) Just like i could say as mass increases obviously its hard for a body to accelarate and we could relate this with real life very easily but I am not able to relate inverse relation of force and displacement when work is constant...
12. ### Problem with the Definition of work

So they are inversely proportional, give me examples, i can not imagine their inverse relation, as force increases,displacement also increases how it will decrease, but direction is also important
13. ### Problem with the Definition of work

From Newton's 2nd law F = ma and a = F/m(acceleration and mass are inversely related when force is constant) But in w = F.d , F =w/d(but d and F are not inversly related just as above) I think there's something wrong in my question, please point it to me or please answer it.
14. ### Question about circular motion and acceleration

Wonderfull explanation, just replace v^2 by v Thank you so much, for this explanation
15. ### Question about circular motion and acceleration

I know that, this is not the magnitude of acceleration, it will be root of the sum of the square of components in both tangential and radical direction, but in v=rω its the total magnitude of the velocity and in a= rα its not the magnitude of total acceleration, its just the magnitude along the...
16. ### Question about circular motion and acceleration

In circular motion 1) V = rw and ##\vec V## = r ω##\vec e_{tan}## 2) a = rα and ##\vec a## = -##\frac{v^2}{r}####\vec e_{rad}## + rα##\vec e_{tan}## Where ##\vec e_{tan}## is the unit vector along the tangent in increasing direction of θ And ##\vec e_{rad}## is the unit vector along the radial...
17. ### B Are the Sun's rays reaching us always parallel?

Thats due to atmospheric refractions, disturbance in their path

19. ### How kinetic friction works

Yes you are right, my confusion has gone now I could solve problem containing two or three surfaces but solving questions containing only two surfaces sometimes makes me confuse but now i am cleared Thanks @jbriggs444 and @anorlunda
20. ### How kinetic friction works

If this fbd is correct then fk is in the direction of accelaration this is why i said its towards acceleration or more precisely its the reason for accelaration due to fbd, but why kinetic friction is helping to acc. In this case
21. ### How kinetic friction works

How would you solve this question: A body slipping on a rough horizontal plane moves with a deceleration of 4m/s^2. What is the coefficient of kinetic friction between the block and plane ? Please note that this is not a HW question I am asking this, because i think that in this case you will...
22. ### How kinetic friction works

@Nidum , sorry i misunderstood your point
23. ### How kinetic friction works

So if surface area is really big then friction will depend on surface area, i think that its approximately independent of surface area because when surface area increases then real area of contact at microscopic level also increases and as real area of contact increases then pressure on...
24. ### How kinetic friction works

@jbriggs444 I have another doubt Is friction always independent of surface area? Its hard to move solid cube then ball of same mass. I think friction depends on real contact area between the surface asperities then the geometric contact between the surface.
25. ### How kinetic friction works

Yes you are right, this is why i said i liked his answer, I didn't said that i agree with him.i posted his answer here to get opinion on his approach,
26. ### How kinetic friction works

Yes you are right, for solving problem this is not required, but i don't know why but questioning concept has become my hobby, even if i don't want to raise a question a question immediately bumps in my head related to the theory part, i want to become theorotical physics and to do so i have to...
27. ### How kinetic friction works

https://physics.stackexchange.com/questions/260979/how-is-frictional-force-dependent-on-normal-reaction/260997#260997 I liked john rennie's answer, what do you think of that?
28. ### How kinetic friction works

Could any budy tell me the intuition behind Why friction is proportional to normal force?
29. ### How kinetic friction works

No budy answered my final question yet Do kinetic friction always acts in opposite direction of motion I think yes, i need more opinions
30. ### How kinetic friction works

So what is making book to accelarate with table as in same direction as table is moving
31. ### How kinetic friction works

I think only kinetic friction is in opposite to the direction of motion, otherwise for example consider two block A and B, A is on B and B is pulled by a force F so both block accelarates with accelaration 'a' in the direction of force but we noticed that there is no force acting on upper block...
32. ### How kinetic friction works

Wow i got it Thanks @BvU and @anorlunda We could also imagine it by keeping one hand stiff and finger stretched out and then moving another hand's finger over the fingers of that hand. So another question raised in my mind, Do kinetic friction always acts in opposite direction of motion?(i am...
33. ### How kinetic friction works

Could anybody explain what happens at the molecular level when one of the two bodies in a contact starts moving w.r.t other, i mean in this process what causes kinetics friction force, i tried myself to think of it but i could not come up with any, so please help me.
34. ### B What do LIGO & VIRGO do?

Wow this sounds interesting
35. ### B What do LIGO & VIRGO do?

I mean do they only detect gravitational waves?, if yes then why spending so much money on this big machine, just to detect something(i know that proving such a beautiful theory is a great achievement), but what next, i mean what other benefits they got after detecting gravitational waves
36. ### Question about inertial and non inertial frames

Yes, discussion is already over :welcome:
37. ### Question about inertial and non inertial frames

Ohh sorry man This answered my question Actully i haven't studied the concept of friction so i was having some misconceptions with friction, sorry for this point less question
38. ### Question about inertial and non inertial frames

Sorry i didn't understand the point I think something is wrong here
39. ### Question about inertial and non inertial frames

This is the point As bus is accelarting so as person A is accelarting with respect to B but person A is not feeling any force then Newtons first law is getting fail in inertial frame I know something is wrong in my statement, so please point it to me
40. ### Question about inertial and non inertial frames

Suppose a person A is standing in a bus and bus is accelerating forward then when a person B standing outside observes A he see that A is accelerating in forward direction then there must be a force acting on him which is making him accelarating(because Newtons first law holds in Earth's frame)...
41. ### A few questions related to tension in a string

This explanation looks righ and it satisfies me but can you provide me the link or any source where this thing is mentioned about the equilibrium.

43. ### A few questions related to tension in a string

Woow man i liked it, "strings can only pull", he was like mazor in military, but he didn't explained why F has to be equal to the tension in the string in his last problem but this video helped me, thanks for wonderfull suggestion.
44. ### A few questions related to tension in a string

From the above article i understood that van-der-waal forces are distance-dependent interactions between atoms or molecules and sometime force acts as attractive and sometimes it acts as repulsive then according to this, for tension to be upward force must be attractive between surface and rope...
45. ### A few questions related to tension in a string

continuation of the problem Solution: I understood the solution but in this solution,we have to assume that pulling force of his friend is same as tension in the string? Why we assumed so, why didn't we took F as force applied by his friends and T as tension in the string separately, why...
46. ### A few questions related to tension in a string

Its getting hard for me to deal with the problems related to tension and reason behind this is not clear understanding of the concept so i have few questions on this. What causes tension in a rope/string(i think its related to electromagnetism, but i am not getting the clear idea behind this)...
47. ### I What if everyone on Earth starts bursting crackers for one day?

What amount of Air and sound pollution would this cause, i mean if every single person on Earth starts bursting crackers for 5-6 hours only for one day, I just need the approximate idea of dammage this would cause to environment, u could assume average values for these data, please help me, i am...
48. ### Question related to inertia and non inertial frame

Does adding of forces in non inertial frame makes force as frame dependent or it is frame independent because psuedo forces are not real In short Is force frame dependent?
49. ### Question related to inertia and non inertial frame

Yes i just posted it in hurry, but i got the answer, i was right from bus reference its fictitious force and from Earth's frame its inertia
50. ### Question related to inertia and non inertial frame

Thanks @jbriggs444 , this made it clearer and also @Dale