Physics: Post your doubts here!

[amina1300]

What ....dont remember tht one.

 

[amina1300]

oh the mg one?

 

[amina1300]

And that Q about ---》 msqrt(2gh1) - .... What was the answer to this?

 

[Hassan (SHT)]

How it can be alpha particle scattering, the hay was some mm thick however gold foil was much thinner possibly some layers of gold atom

 

[Hassan (SHT)]

I think it was conservation of momentum

 

[amina1300]

I think it was conservation of momentum

well most end questions r related to nuclear sec but donno whats correct.

 

[Metallic9896]

Guys lol is it cool we discussing answers? I'll give my input for the ones you mentioned:

First question B for certian, every 'smart' kid I know chose B lol, I happened to choose that too.

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Q9 table is similar to this from 2015 qp_12:


Newton’s third law of motion is often summarised as ‘Every action (force) has an equal and
opposite reaction.’

A book rests on a table.

If the weight of the book is the ‘action’ force, what is the ‘reaction’ force?

A the pull of the book on the Earth
B the pull of the Earth on the book
C the push of the book on the table
D the push of the table on the book

Answer is A, which makes sense cause action reaction pairs are the SAME TYPE of force, so it HAD to be a gravitational force, and they act on DIFFERENT objects, so weight of book on Earth = weight of Earth on book. Now the question is, I chose D thinking about this but I may have misread the options. The options in our question were stated as 'the force on _______ from _____' so if D was force on Earth from book then it was D but if it was force on book from Earth then I probably messed it up and it was A or B or something, the one which would have force on Earth from book.

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38 was alpha scattering for two reasons: 1. Last qs focus on nuclear 2. it was a demonstration and the idea was to show how a bullet would mostly pass through but some would be deflected by a ball i.e. the nucleus, bullets were alpha particles. The dimensions may not be as accurate but still the idea was shown as the total area was in meters while ball were in centimetres. It couldn't be momemtum there was no means of measuring velocity.

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That q about sqrtmgh was C, the sum of m sqrt 2gh1 and m sqrt 2gh2

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The one about air resistance was C, the scary looking equations. I got it wrong.

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Diameter of wire in which we had two different resistivities was 0.57 (nm?)

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Torque one was 9.2

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Hmm it was between Q and S, the vertial ones, where on left side resistors would add up as 8 + 2 = 10 and right would add up as 4 + 6 = 10, the total came out to be 5, which was highest. Option A gave 1.8 total, this was B, C and D gave 4.2 and 4.8 I think.

 

[Zaki ali asghar]

I think the Q read as W is the force exerted by book on the table

 

[Metallic9896]

I think the Q read as W is the force exerted by book on the table

Ah okay you sure? In that case I'm wrong.

 

[amina1300]

I remember it was "W" is the force...... but, wasn't it suppose to be D?

 

[Metallic9896]

I remember it was "W" is the force...... but, wasn't it suppose to be D?

LOL I chose D. I hope it's correct. It would be if:

1. Zaki doesn't remember right and W was just the weight as in the 2015 question
2. Option D said 'force on Earth from book"

 

[Zaki ali asghar]

What was the answer to the total number of maxima formed?

 

[Metallic9896]

What was the answer to the total number of maxima formed?

8

3.5 in top half 3.5 in bottom half = 7 + 1 central = 8

 

[Zaki ali asghar]

No thats not how its done,the ans was 3.5.You dont round up to nearest integer for maxima,3 at the top 3 at bottom and one central so total of 7.

 

[Minsa Fatima]

8

3.5 in top half 3.5 in bottom half = 7 + 1 central = 8

Shouldnt that be in whole numbers? 2*3 +1=7

 

[amina1300]

LOL I chose D. I hope it's correct. It would be if:

1. Zaki doesn't remember right and W was just the weight as in the 2015 question
2. Option D said 'force on Earth from book"

Oh that was D I chose the option with the force of table on book, whatever option that was There is some exam paper of before 2013 with that same question I remember it now as I got it in my school exam paper 2 times and I always used to do it wrong by choosing what you chose. Im still confused as to whether Im correct now or not!

 

[Zaki ali asghar]

What about the graph question which was a friction less slope?

 

[amina1300]

8

3.5 in top half 3.5 in bottom half = 7 + 1 central = 8

I guess I wrote 6 in this one hmm... didn't know how to solve it. but what I do know that 3.5 becomes 3 +3 +1 ---> 7.

 

[Metallic9896]

No thats not how its done,the ans was 3.5.You dont round up to nearest integer for maxima,3 at the top 3 at bottom and one central so total of 7.

Ah darn it I know I know idk what I did lol I did a similar question that bothered my friends yesterday without any problem dunno what happened in the paper. Lol

 

[Metallic9896]

I guess I wrote 6 in this one hmm... didn't know how to solve it. but what I do know that 3.5 becomes 3 +3 +1 ---> 7.

3.5 means 3 whole maximas. The 0.5 won't count. But that 3 whole means on 90 degrees in top half. So you x2 = 6 total maximas at angles, and 1 central at 0 angle which you have to count anyway so 7.