Physics: Post your doubts here!

[i_try9621]

It is mentioned in the question that upwards is considered positive. We know that acceleration due to gravity is always downwards, so it should be taken as negative. And since that acceleration is constant throughout the motion, its value doesn't change.

Got it! Thanks

 

[i_try9621]

Might be a stupid question, but still need help with this one. The confusion is how exactly are we supposed to find a best estimate in such cases . The answer's "B"
http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Physics (9702)/9702_s05_qp_1.pdf

 

[Shujaat Khan]

see solution 752 at
http://physics-ref.blogspot.com/2015/05/physics-9702-doubts-help-page-152.html

Hey wanted to tell you this, you may not remember me. I was having troubles in physics last year and you really helped me a lot( especially with your blog)
Finally my C in mock exams went to an A in cambridge exams in physics, really thanks a lot man.
Your way of solving questions make it so easy to understand, you should definitely keep it up, even my teacher can't explain as better as you.

 

[i_try9621]

see solution 752 at
http://physics-ref.blogspot.com/2015/05/physics-9702-doubts-help-page-152.html

Thanks for that!

 

[ashcull14]

b)(i) is a direct question. The plates must be parallel so that the field is uniform; and horizontal so that the field is vertical. (Since the experiment involves finding the charge on the oil drop by balancing the electric force and gravitational force acting on it.)

c) All these values are small integer multiples of a certain base value, which is equal to 1.6*10^-19 and is the negative of the charge of an electron. (This was proposed by the Millikan oil drop experiment. I am not sure of the details to this.)

thanks

 

[ashcull14]

 

[Hassan Ali Abid]

View attachment 59162

 

[nehaoscar]

View attachment 59162

substitute w = 2pi/t
And t of the earth is one orbit i.e 1 day
1 day = 24*60*60 seconds

 

[The Sarcastic Retard]

http://studyguide.pk/Past Papers/CIE/International A And AS Level/9702 - Physics/9702_w09_qp_42.pdf

please help me with question 3(c) [ the answer on the mark scheme is - straight line between(-0.3,+190) and (+0.3,-190)]

I don't know how they got 190 ms^-2 as the y coordinate. Thank you so much in advance!!

Read the question, its mentioned that frequency is now half of the one we measured in (b) so that is 250/2 = 125Hz
Now use this frequency, values of x and calculate respective acceleration.

 

[m10cr7]

this is question number 4 part c of paper 41 nov 2014. what is the shape of the required curve

Paper = http://papers.xtremepapers.com/CIE/...nd AS Level/Physics (9702)/9702_w14_qp_41.pdf

Mark Scheme =
http://papers.xtremepapers.com/CIE/...nd AS Level/Physics (9702)/9702_w14_ms_41.pdf

 

[The Sarcastic Retard]

http://studyguide.pk/Past Papers/CIE/International A And AS Level/9702 - Physics/9702_w10_qp_42.pdf
Q3(c) explanation with graph required. Is it related to damping thingy?
Just correct me, if I am wrong.
Due to a slight weight, there will be some damping, so the frequency remains same as damping doesnt affect time period so doesnt affect frequency. And due to damping the curve will be slightly flatter and lower than original amplitude?

Thanks.

 

[The Sarcastic Retard]

View attachment 59192
this is question number 4 part c of paper 41 nov 2014. what is the shape of the required curve

Paper = http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Physics (9702)/9702_w14_qp_41.pdf

Mark Scheme =
http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Physics (9702)/9702_w14_ms_41.pdf

Amplitude will start decreasing so the curve's amplitude will decrease slightly in each oscillations and come to rest due to damping. Here we are asked to draw for 2 oscillations with the effect of damping, hence the time period will be similar to the orignal graph as damping has no effect on time intervals, and the peak will decreases slowly so curve will be under the loops, this is what marking scheme explains.

 

[Konstantino Nikolas]

http://studyguide.pk/Past Papers/CIE/International A And AS Level/9702 - Physics/9702_w10_qp_42.pdf
Q3(c) explanation with graph required. Is it related to damping thingy?
Just correct me, if I am wrong.
Due to a slight weight, there will be some damping, so the frequency remains same as damping doesnt affect time period so doesnt affect frequency. And due to damping the curve will be slightly flatter and lower than original amplitude?

Thanks.

ur right
the graph is shown in http://physics-ref.blogspot.in/2015/08/physics-9702-doubts-help-page-192.html soln 934

 

[Konstantino Nikolas]

Q1.b
http://papers.gceguide.com/A Levels/Physics (9702)/9702_y16_sp_4.pdf
ms http://papers.gceguide.com/A Levels/Physics (9702)/9702_y16_sm_4.pdf
How is resultant force the difference in gravitational force of Earth and centripetal force of an object on the earth?

 

[donewithtime80]

http://papers.gceguide.com/A Levels/Physics (9702)/9702_w15_qp_53.pdf

qs 2(a)...pls show how to find the gradiesnt

 

[Konstantino Nikolas]

http://papers.gceguide.com/A Levels/Physics (9702)/9702_w15_qp_53.pdf

qs 2(a)...pls show how to find the gradiesnt

v^2 is plotted against r ... so make v^2 the subject of your eqn -> v^2 = Pgr/m
So from that we know the graph is a straight line as it is in the form y=mx+c .... where y = v^2 ; x = r ; c = o (that's why there's no c term) and gradient = Pg/m (the coefficient of x)

 

[donewithtime80]

v^2 is plotted against r ... so make v^2 the subject of your eqn -> v^2 = Pgr/m
So from that we know the graph is a straight line as it is in the form y=mx+c .... where y = v^2 ; x = r ; c = o (that's why there's no c term) and gradient = Pg/m (the coefficient of x)

ohhh got it
thank you

 

[Konstantino Nikolas]

ohhh got it
thank you

no problem mate

 

[Fahad Afzal]

http://papers.xtremepapers.com/CIE/...nd AS Level/Physics (9702)/9702_s12_qp_41.pdf
Q6 (c) Anyone? How can we obtain the average p.d.?

Thanks in advance for your help

 

[The Sarcastic Retard]

http://studyguide.pk/Past Papers/CIE/International A And AS Level/9702 - Physics/9702_s08_qp_4.pdf
3b(ii)

http://studyguide.pk/Past Papers/CIE/International A And AS Level/9702 - Physics/9702_s06_qp_4.pdf
4(a(i)) (c)

http://studyguide.pk/Past Papers/CIE/International A And AS Level/9702 - Physics/9702_w08_qp_4.pdf
3(b)(ii)1 (c(ii))