Physics: Post your doubts here!

[Salonee B]

u = 1.66 x 10^-27
Mass of hellium is 4u = 4 x 1.66 x 10^-27
Like 100km = 100000m.

thank you so, so much!!

 

[ashcull14]

 

[zeejay]

Hey can anyone tell me that why do we use average force for strain energy i.e 1/2×F×e2
.....i mean isn't the extension produced by the full force rather than half the force (average force)....pls help me asap...thanks in advance ✊

 

[awesomaholic101]

Hey can anyone tell me that why do we use average force for strain energy i.e 1/2×F×e2
.....i mean isn't the extension produced by the full force rather than half the force (average force)....pls help me asap...thanks in advance ✊

The work done is basically the area under the graph ... And its a triangle so the formula works that way.
Practically speaking, if we use force at any given point, we'd only be calculating the energy held at that particular point ... Like the instantaneous energy or sth ... So we need to take avg force to calc the overall strain energy held by the spring.

I'm not 100% sure abt this ... So if anyone can confirm, it wud be good.

 

[HappyFlora]

kindly help me out in part bii pleaseee!
Physicist

 

[My Name]

http://papers.xtremepapers.com/CIE/...nd AS Level/Physics (9702)/9702_s11_qp_23.pdf

question 5 part c part iv

MS-(iv) horizontal line through central section of wave ?

http://papers.xtremepapers.com/CIE/...nd AS Level/Physics (9702)/9702_s11_qp_21.pdf

question 7 part b part ii

MS- (ii) lamp with viewing screen on opposite side of tank

means of freezing picture e.g. strobe ?

 

[Rizwan Javed]

http://papers.xtremepapers.com/CIE/...nd AS Level/Physics (9702)/9702_s11_qp_23.pdf

question 5 part c part iv

MS-(iv) horizontal line through central section of wave ?

0.25T corresponds to a quarter cycle. So the new position will be as shown by the red line.

 

[My Name]

View attachment 58954
0.25T corresponds to a quarter cycle. So the new position will be as shown by the red line.

I know what a horizontal line is. I don't get why.

 

[Rizwan Javed]

I know what a horizontal line is. I don't get why.

Lol.


consider the point X. the blue line + green line + orange line + purple line = one cycle.

0.25 = quarter cycle.

so quarter cycle = blue line only.

if you do the same for all the other points on the wave, you'll see that after quarter cycle all the points will lie on the red line.

I hope i'm successful this time

 

[My Name]

Lol.

View attachment 58955
consider the point X. the blue line + green line + orange line + purple line = one cycle.

0.25 = quarter cycle.

so quarter cycle = blue line only.

if you do the same for all the other points on the wave, you'll see that after quarter cycle all the points will lie on the red line.

I hope i'm successful this time

Yes,thank you for taking the time!

 

[donewithtime80]

http://www.cie.org.uk/images/164932-2016-specimen-paper-4.pdf

question 3 b please....please explain the mark scheme answer below...

ans: (b) (i) forces in springs are k(e + x) and k(e – x) C1 resultant = k(e + x) − k(e – x) M1 = 2kx

 

[ashcull14]

HELLO ANYONE??????????????????????????

 

[misscute406]

a_wiserME!! NotYourType check page 1!!

 

[a_wiserME!!]

why will the change in potential energy and the change in kinetic energy be equal??

 

[Konstantino Nikolas]

View attachment 58997

why will the change in potential energy and the change in kinetic energy be equal??

Conservation of energy. Total energy of an isolated system remains same (all forms in which energy is lost will be gained in other forms).
Here, there are only two energies that we need to consider, i.e, the kinetic energy and electric potential energy ... so loss in one equals the gain in other.

 

[The Sarcastic Retard]

b(ii), d(i)(ii) someone please explain it to me.. Thanks.

 

[Konstantino Nikolas]

View attachment 58957
HELLO ANYONE??????????????????????????

Which part exactly do you not get?

 

[The Sarcastic Retard]

View attachment 59007View attachment 59008View attachment 59009
b(ii), d(i)(ii) someone please explain it to me.. Thanks.

Well I got it.

 

[a_wiserME!!]

Conservation of energy. Total energy of an isolated system remains same (all forms in which energy is lost will be gained in other forms).
Here, there are only two energies that we need to consider, i.e, the kinetic energy and electric potential energy ... so loss in one equals the gain in other.

thnx.. but can you pls help with the calculation part??

 

[Konstantino Nikolas]

thnx.. but can you pls help with the calculation part??

Oh sorry, I thought you didn't get only the energy part.
Anyway, see solution 559 on this page : http://physics-ref.blogspot.in/2015/04/physics-9702-doubts-help-page-109.html
They've given the calculations with the explanation.