Physics: Post your doubts here!

[Sariya Khan]

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)

It maybe considered as e.c.f. 'error carried forward' , and you may lose 1-2 marks at maximum

 

[nadeen64]

Can someone please explain these two questions? theyre both D.

 

[Sariya Khan]

Can someone please explain these two questions? theyre both D.
View attachment 60627
View attachment 60628

In order to fly North.. He has got to steer in a way that cancels the effect of wind. So the leftward velocity has got to be 85.0 kmh-1.
So, the angle that it makes with the north is going to be : sin-1(85.0/200) =25.2 degrees

 

[Rizwan Javed]

Can someone please explain these two questions? theyre both D.
View attachment 60627
View attachment 60628

For the second MCQ, just flip the wave and you'll get the answer. Flip it like this:

 

[nadeen64]

For the second MCQ, just flip the wave and you'll get the answer. Flip it like this:

View attachment 60629

why do we flip it tho?

 

[Umair Abid]

It maybe considered as e.c.f. 'error carried forward' , and you may lose 1-2 marks at maximum

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

 

[Awesome12]

9702_s15_qp_12.pdf
Can somebody explain question 6. Answer is C
And Question 36. Answer is B

 

[Umair Abid]

9702_s15_qp_12.pdf
Can somebody explain question 6. Answer is C
And Question 36. Answer is B

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%

 

[Umair Abid]

9702_s15_qp_12.pdf
Can somebody explain question 6. Answer is C
And Question 36. Answer is B

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.

 

[Sariya Khan]

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

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!

 

[Umair Abid]

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!

Thanks, that's reassuring.

 

[Awesome12]

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.

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

 

[Umair Abid]

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

Yeah sorry, it is 9V. My bad.

 

[The Sarcastic Retard]

Site is back

 

[i_try9621]

Someone help me with this. Answer for this is D. It's from 9702/12/M/J/15

 

[qwertypoiu]

View attachment 60689 Someone help me with this. Answer for this is D. It's from 9702/12/M/J/15

s = ut + 1/2 * at^2
u = 0
s = 1/2 * at^2
a = 2s / t^2
g = 2h/ t^2

For g to be large, either h is larger or t is smaller. Only D satisfies this.

 

[AnonymousX9]

Guys pls help with this one^

 

[qwertypoiu]

Guys pls help with this one^

D?

 

[AnonymousX9]

D?

Yes, it is D. How? I don't get it.

 

[Saad the Paki]

Yes, it is D. How? I don't get it.

Consider anti clockwise direction of current as positive. Current leaves V1 from +ve terminal and goes in the anti clockwise direction. However V2 and V3 push current in THE CLOCKWISE direction which is opposite to V1.
So thus V1 will be positive and V2 & V3 will be negative.
V1-V2-V3 . Thus option D is correct