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Physics: Post your doubts here!

Konstantino Nikolas

Konstantino Nikolas

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i_try9621 said:
Mark scheme says it's "B"
wait so isn't acceleration supposed to be positive when it's falling ?
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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.
 
Mr. Stamina

Mr. Stamina

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Can someone please upload the in chapter answers, because I have trouble with electromagnetic induction my book is the secondary edition
 
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Salonee B

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Q. A small ball moves from rest down plane RA and then rises up plane LA. It then moves down plane LA and rises up plane RA to its original height. The motion repeats itself. State and explain whether the motion of the ball is simple harmonic.

A. mark scheme says "acceleration is constant (magnitude) so cannot be s.h.m."

I still dont get it, how is acceleration constant? doesnt it come to equilibrium position where x=0 and a=0? I know this question sounds dumb, but thanks to anyone that helps in advance!
 
Konstantino Nikolas

Konstantino Nikolas

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Salonee B said:
Q. A small ball moves from rest down plane RA and then rises up plane LA. It then moves down plane LA and rises up plane RA to its original height. The motion repeats itself. State and explain whether the motion of the ball is simple harmonic.

A. mark scheme says "acceleration is constant (magnitude) so cannot be s.h.m."

I still dont get it, how is acceleration constant? doesnt it come to equilibrium position where x=0 and a=0? I know this question sounds dumb, but thanks to anyone that helps in advance!
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The ball is only released from rest. No external forces are given. So the acceleration is only due to gravity = gsinθ acting along the plane; this remains constant throughout the motion. Therefore, it's not shm.
 
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Shujaat Khan

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Physicist said:
see solution 752 at
http://physics-ref.blogspot.com/2015/05/physics-9702-doubts-help-page-152.html
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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.
 
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ashcull14

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Konstantino Nikolas said:
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.)
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thanks :)
 
The Sarcastic Retard

The Sarcastic Retard

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Salonee B said:
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!!
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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.
 
The Sarcastic Retard

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The Sarcastic Retard

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m10cr7 said:
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
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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. :)
 
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Konstantino Nikolas

Konstantino Nikolas

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