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Physics: Post your doubts here!

Bhaijan

Bhaijan

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9702_s09_qp 1
Ans is C
im confused there are two types of beta decay
someone please explain the answer
Qupload_2016-5-21_19-25-27.png
 
Saad the Paki

Saad the Paki

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Bhaijan said:
9702_s09_qp 1
Ans is C
im confused there are two types of beta decay
someone please explain the answer
QView attachment 60625
Click to expand...
In the old syllabuses, there was only one type of Beta decay,which is B- decay . So whenever they mention beta decay we will assume it to be B- .

So in B- neutron decays to proton increasing the proton number while keeping nucleon number the same. But this question is backwards. So it must have one less proton to form this Calcium nuclide. So ans should be C
 
Bhaijan

Bhaijan

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upload_2016-5-21_19-52-8.png


The question is from 9702_s09_qp_1 and the answer is B.
In my opinion the answer should have been C because if we were to consider the water on both the tanks and their heights, the total PE would come out to be mgh/2. If we were to subtract this from the original height, the loss would come out to be mgh/2. [All this is done if we were to assume that the new height of the water in each tank would be 1/2h]
 
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U

Umair Abid

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Yeah so I made a huge blunder in my Physics paper 3 practical exam. Instead of measuring and recording length of x in question 1, I measured it from the opposite side so my readings are kind of 1-x rather than x. This did mess up my trend in graph as well.

Up to how many marks will I lose for the table and the graph because of this?

(Since no one replies in threads, I'll post this here xD)
 
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Hania Ahmer

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Two copper wires connected in parallel, one wire is thick n other is thin, why is drift velocity same in both? (According to pacific phy) ..oh and assuming a constant temperature...
 
Sariya Khan

Sariya Khan

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Umair Abid said:
Yeah so I made a huge blunder in my Physics paper 3 practical exam. Instead of measuring and recording length of x in question 1, I measured it from the opposite side so my readings are kind of 1-x rather than x. This did mess up my trend in graph as well.

Up to how many marks will I lose for the table and the graph because of this?

(Since no one replies in threads, I'll post this here xD)
Click to expand...
It maybe considered as e.c.f. 'error carried forward' , and you may lose 1-2 marks at maximum :)
 
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Umair Abid

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Sariya Khan said:
It maybe considered as e.c.f. 'error carried forward' , and you may lose 1-2 marks at maximum :)
Click to expand...
Your reply really made my day but this is question 1 we are talking about. My trend in graph is opposite and the whole table of results has wrong values of x (other calculations, decimal places, s.f, column titles with there units are perfectly fine though). My Sir said that I may loose upto 5-6 marks for this. Well either way, I'll be trying my best for paper 1. Thanks for replying :)
 
U

Umair Abid

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Awesome12 said:
9702_s15_qp_12.pdf
Can somebody explain question 6. Answer is C
And Question 36. Answer is B
Click to expand...
Question 6: Original length is 0.8+0.2 because of systematic error, it appeared less. Uncertainties are added up so 0.02mm + 0.02mm = 0.04 total uncertainity. UC % = 0.04/1.0 * 100 = 4%
 
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Umair Abid

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Awesome12 said:
9702_s15_qp_12.pdf
Can somebody explain question 6. Answer is C
And Question 36. Answer is B
Click to expand...
For question 36, the slider is fitted with 3 Ohm resistor so think of it as something as that can move above or below the 3 Ohm resistor but not move as far as to the other resistors.
The 4 Ohm resistor will have a P.d of 4V across it according to the P.d formula: 4/(4+3+2) * 12
So 5V from total will be left, the 3 Ohm resistor will have P.d 3V across it so 2V will be left from the total. The last 2V will be the P.d across the 2 Ohm resistor. Here's a pic for better understanding. Think of blue lines as far as the slider can go.

1ROhAM9.png
 
Sariya Khan

Sariya Khan

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Umair Abid said:
Your reply really made my day but this is question 1 we are talking about. My trend in graph is opposite and the whole table of results has wrong values of x (other calculations, decimal places, s.f, column titles with there units are perfectly fine though). My Sir said that I may loose upto 5-6 marks for this. Well either way, I'll be trying my best for paper 1. Thanks for replying :)
Click to expand...
My teacher told me that. And he's been teaching since 2005. You won't lose marks in graph. Because you already took your values of x to be opposite of what was required. Hope this suffices your query! :)
 
A

Awesome12

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Umair Abid said:
For question 36, the slider is fitted with 3 Ohm resistor so think of it as something as that can move above or below the 3 Ohm resistor but not move as far as to the other resistors.
The 4 Ohm resistor will have a P.d of 4V across it according to the P.d formula: 4/(4+3+2) * 12
So 5V from total will be left, the 3 Ohm resistor will have P.d 3V across it so 2V will be left from the total. The last 2V will be the P.d across the 2 Ohm resistor. Here's a pic for better understanding. Think of blue lines as far as the slider can go.

1ROhAM9.png
Click to expand...
Where did the 12 come from. Shouldnt it be 9?

I did it as follows:
Lowest :
(2/2+4+3) * 9 = 2V and
Highest :
(5/2+4+3) * 9 = 5V

Anyways thanks for both the explanations
 
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