Physics: Post your doubts here!

[ashcull14]

I mean what u dont get in the explanation part??
Work done = F*change in x.
Work done = Ep
Ep = F * 4 * 10^-2
This was the first way.
We know Ep = GMm/r
Now we know radius increases every year by 4cm.
So we know radius is changing so we can use the formula Ep = GMm(1/r1 - 1/r2)
r1 = orignal radius
r2 = 4 * 10^-2
This was the second way explained.

Now I asked u, what u dont get in this explanation, I will clear that..

k i knw tht was dumb ..i got it ..ty

 

[The Sarcastic Retard]

k i knw tht was dumb ..i got it ..ty

Doubt is a doubt!
No problem ^_^

 

[Mahnoorfatima]

I mean what u dont get in the explanation part??
Work done = F*change in x.
Work done = Ep
Ep = F * 4 * 10^-2
This was the first way.
We know Ep = GMm/r
Now we know radius increases every year by 4cm.
So we know radius is changing so we can use the formula Ep = GMm(1/r1 - 1/r2)
r1 = orignal radius
r2 = 4 * 10^-2
This was the second way explained.

Now I asked u, what u dont get in this explanation, I will clear that..

isn't r2 supposed to be 4*10^-2 + r1? As it says 4cm is added to it every year? :/

 

[The Sarcastic Retard]

isn't r2 supposed to be 4*10^-2 + r1? As it says 4cm is added to it every year? :/

Oh yes!! A silly error! Thanks for that, I will add it to my explanation.
ashcull14 see this!! A small mistake can cost heck loads of marks!!

 

[Mahnoorfatima]

SOMEBODY PLSSSS

 

[The Sarcastic Retard]

View attachment 60501
SOMEBODY PLSSSS

what is the b part?

 

[ashcull14]

Oh yes!! A silly error! Thanks for that, I will add it to my explanation.
ashcull14 see this!! A small mistake can cost heck loads of marks!!

haha...yea i noticed it aswell ...but i got it already do doesnt matter

 

[qwertypoiu]

It is October/November 2012 paper 41. I can't link it because the site is not working. And one other thing, kinetic energy (temperature) of gas molecules only and only increase if the particles collide with more speed right? It has nothing to do with how often the molecules collide, for example in less space(when pressure is increased) ?

That student said internal energy is DOUBLED if temperature increases from 100 to 200 degrees. This is wrong.
Initial temperature = 373K
Final temperature = 473K
So if anything, the internal energy will increase by a proportionality constant of 473/373.

 

[Mahnoorfatima]

what is the b part?

Oh I'm so sorry

 

[Mahnoorfatima]

That student said internal energy is DOUBLED if temperature increases from 100 to 200 degrees. This is wrong.
Initial temperature = 373K
Final temperature = 473K
So if anything, the internal energy will increase by a proportionality constant of 473/373.

Oh right!!!! Thanks a lot for clearing it up! I got confused when I saw the MS say that it's wrong because the temperature is in degree Celsius not kelvin.

 

[Mahnoorfatima]

There's this question in MJ 11 P41, where a transformer is given and the secondary coil is connected to a load resistor, and the question says "use faradays law to explain why the P.d across the load and the e.m.f of the supply are not in phase? How do I use faradays law in this?! Faradays law just states the direct proportionality between the induced e.m.f and the flux linkage, it has nothing to do with the direction, no ? It's Lenzs' law that says the induced emf will be in a direction such that it opposes the change producing it.. :/ what is this???! Someoneeee this too pliss

 

[The Sarcastic Retard]

Oh I'm so sorry View attachment 60502

I will explain in short, I am in hurry..
Look the wavelength u calculate in b is not in the range of 400 to 700.
So as its continuous spectrum two dark lines shows two lines absorbed that are other two wavelengths.
The spectrum will be a scatterd one due to the emergence of photons from the gas. as electron jumps from excited state.

 

[Mahnoorfatima]

I will explain in short, I am in hurry..
Look the wavelength u calculate in b is not in the range of 400 to 700.
So as its continuous spectrum two dark lines shows two lines absorbed that are other two wavelengths.
The spectrum will be a scatterd one due to the emergence of photons from the gas. as electron jumps from excited state.

Thanks a bunch! but I didn't get the last part why would it be a scattered one? Only one line will pass through the cloud and two dark lines will show absorption. What about the scatter?

 

[The Sarcastic Retard]

There's this question in MJ 11 P41, where a transformer is given and the secondary coil is connected to a load resistor, and the question says "use faradays law to explain why the P.d across the load and the e.m.f of the supply are not in phase? How do I use faradays law in this?! Faradays law just states the direct proportionality between the induced e.m.f and the flux linkage, it has nothing to do with the direction, no ? It's Lenzs' law that says the induced emf will be in a direction such that it opposes the change producing it.. :/ what is this???! Someoneeee this too pliss

b(ii)

 

[The Sarcastic Retard]

Thanks a bunch! but I didn't get the last part why would it be a scattered one? Only one line will pass through the cloud and two dark lines will show absorption. What about the scatter?

I am in hurry, hope u get an idea with this.

 

[Mahnoorfatima]

I am in hurry, hope u get an idea with this.
View attachment 60504

I did! Thank you!

 

[Mahnoorfatima]

How do I answer this question..? :3

 

[Mahnoorfatima]

Can someone tell me if I get 3 marks in this question? Explain how the line spectrum of hydrogen provides evidence for the existence of discrete electron energy levels in atoms.
Ans. Each atom will have different energy levels which indicate the transition of an electron from a higher to a lower energy level emitting discrete wavelengths of photons. The wavelengths emitted will be unique to that atom only.

 

[qwertypoiu]

Can someone tell me if I get 3 marks in this question? Explain how the line spectrum of hydrogen provides evidence for the existence of discrete electron energy levels in atoms.
Ans. Each atom will have different energy levels which indicate the transition of an electron from a higher to a lower energy level emitting discrete wavelengths of photons. The wavelengths emitted will be unique to that atom only.

I think what the question really wants you to say (I could be wrong) is that there are DISTINCT bands in the line spectra. It's not like ALL wavelengths of light were absorbed, but rather distinct, specific ones.

You have to be careful with the wording of the question. They said: "Explain how the line spectrum of hydrogen provides evidence for..."
So you HAVE to talk about the APPEARANCE of the spectrum itself. Hope I'm making sense.

Spoiler

 

[waqas123]

Can someone explain this to me?