Physics: Post your doubts here!

[Catherine_1]

Please help!

 

[OmarKhan99]

View attachment 59340

Thanks a lot.
But why do the red and yellow lines have different gradients?

 

[Konstantino Nikolas]

Thanks a lot.
But why do the red and yellow lines have different gradients?

I forgot the question. But if the gradient of velocity-time graph is different it means the acceleration of motion at those times are different.

 

[Wâlèé Atèéq]

Than

This has summary of the topics:
https://www.xtremepapers.com/community/threads/as-and-a2-physics-summaries.42827/

Thanx Dude..!

 

[Eugene99]

Is Physics harder than Chemistry? I'll be taking AS Physics in Nov of 2016, since I'm taking AS Chemistry, Biology and Mathematics this summer, I was wondering whether I'll find Physics even harder than Chemistry or is it better than that?

 

[nehaoscar]

Than

Thanx Dude..!

Welcome

 

[Konstantino Nikolas]

Is Physics harder than Chemistry? I'll be taking AS Physics in Nov of 2016, since I'm taking AS Chemistry, Biology and Mathematics this summer, I was wondering whether I'll find Physics even harder than Chemistry or is it better than that?

Depends on which you have more interest in really. And they are two totally different subjects so dunno if we can compare their difficulty level. But I find chemistry questions more complicated than in physics ... especially AS.

 

[Eugene99]

Depends on which you have more interest in really. And they are two totally different subjects so dunno if we can compare their difficulty level. But I find chemistry questions more complicated than in physics ... especially AS.

I understand...and I think I'm better interested in Physics than in chemistry! Chemistry is just a helll!!
which subs are you taking?

 

[OmarKhan99]

I forgot the question. But if the gradient of velocity-time graph is different it means the acceleration of motion at those times are different.

Yes I know that. Can you please tell me why are the accelerations different?

This is the question

 

[Konstantino Nikolas]

Yes I know that. Can you please tell me why are the accelerations different?

This is the question

Ah yeah, it's this question.

Once the string is cut, the log doesn't immediately fall down. (I believe you understood that.) In the log's motion upward after the string is cut, there is friction acting on the same side as the component of weight - along the slope. So the addition of both forces divided by the mass of the log would give you acceleration.
On the other hand, once the log reaches a zero velocity, that is the maximum height it can go up to. Then, it starts falling down. In this part of its motion, the component of weight along the slope is opposed by the friction. So, acceleration would be the difference in both forces over the mass of the log.
Hence, the two accelerations are different and you get two different v-t gradients.

Hope you got it.

 

[Konstantino Nikolas]

I understand...and I think I'm better interested in Physics than in chemistry! Chemistry is just a helll!!
which subs are you taking?

Oh well then definitely you would find physics easier.
Chem phy math and eng.

 

[Syed Fakhar Hussain]

Few days back i searched every website i knew, no where a yearly binder with marks schemes was available.
When i was tired of finding thought why don't make one and help others.
Took me 4 hours but yes i made it .

Find it here :
https://www.dropbox.com/s/2qooifqxgpu47cq/P4 MJ_02-ON_15 (YEARLY).pdf?dl=0
_____________________________________________
__________________________________
_________________________
Time is precious waste it wisely.

 

[Syed Umar]

Few days back i searched every website i knew, no where a yearly binder with marks schemes was available.
When i was tired of finding thought why don't make one and help others.
Took me 4 hours but yes i made it .
_____________________________________________
__________________________________
_________________________
Time is precious waste it wisely.

Great.
Are you going to upload here?

 

[Syed Fakhar Hussain]

Great.
Are you going to upload here?

I am going to share a dropbox link in 5 mins just wait.

 

[nehaoscar]

View attachment 59421
Hey,
Could anyone please provide me with the reasoning for the following questions of the photoelectric effect:
a) In graph 2 why does increase in frequency cause current to increase at a decreasing rate?
b)In graph 3 and 4 , what does negative stopping potential imply?Like what exactly does it mean?

Please help.

a - photoelectric current is the no. of photons hitting the metal causing emission - so it's dependent on intensity and not frequency (E=hf) so as f becomes greater than threshold f, current increases until some time after which it'll become constant as intensity will be constant
b - check here http://www.s-cool.co.uk/a-level/phy.../photoelectric-current-and-stopping-potential

 

[nehaoscar]

View attachment 59440
View attachment 59441

View attachment 59442
View attachment 59443

Please help!

http://physics-ref.blogspot.in/2014/11/physics-9702-doubts-help-page-20.html
See 106

 

[Catherine_1]

http://physics-ref.blogspot.in/2014/11/physics-9702-doubts-help-page-20.html
See 106

Thank youuu!

 

[Catherine_1]

a - photoelectric current is the no. of photons hitting the metal causing emission - so it's dependent on intensity and not frequency (E=hf) so as f becomes greater than threshold f, current increases until some time after which it'll become constant as intensity will be constant
b - check here http://www.s-cool.co.uk/a-level/phy.../photoelectric-current-and-stopping-potential

Thank youuu once again! But I have a slight query if it depends on intensity then why does increase in frequency trigger initially an increase in current? Like, The way I am seeing: when we increase the frequency the electrons gain more ke so the flow faster and since current is the rate of flow of charged particles it increases.However,eventually what happens is that intensity affects the number of electrons emitted per unit time(I am right?:/ ) so since intensity is constant the current turns out to be constant as nos of electrons are same. Is my analysis correct? I am confused slightly?:/

Oh and yeah the following seems a pretty silly question but the contradictory nature is perplexing me. If you have an answer as to what would be ideal?

Somehow the answers are contradictory in nature.:/ Should the answer simply be a bright spot?

Thank you.

 

[nehaoscar]

Thank youuu once again! But I have a slight query if it depends on intensity then why does increase in frequency trigger initially an increase in current? Like, The way I am seeing: when we increase the frequency the electrons gain more ke so the flow faster and since current is the rate of flow of charged particles it increases.However,eventually what happens is that intensity affects the number of electrons emitted per unit time(I am right?:/ ) so since intensity is constant the current turns out to be constant as nos of electrons are same. Is my analysis correct? I am confused slightly?:/

Oh and yeah the following seems a pretty silly question but the contradictory nature is perplexing me. If you have an answer as to what would be ideal?

Somehow the answers are contradictory in nature.:/ Should the answer simply be a bright spot?

Thank you.

Yeah the way you're writing it seems right since eventually the intensity is constant so no. of e- emitted is constant so the current will be constant
so yep
And for the other question that you've posted I have no idea xP

 

[Catherine_1]

Yeah the way you're writing it seems right since eventually the intensity is constant so no. of e- emitted is constant so the current will be constant
so yep
And for the other question that you've posted I have no idea xP

Thank youuu. Cool, lol no problem.