Physics: Post your doubts here!

[qwertypoiu]

Oh thank you so much!
Would appreciate it if u could help in this one as well ( Q6 )

P = I^2 * R
So percentage uncertainty in P = 2 * percentage uncertainty in I + percentage uncertainty in R

Percentage uncertainty in I = 0.05/2.5 * 100% = 2%
Percentage uncertainty in R = 2% (given in question)
Percentage uncertainty in P = 2*2% + 2% = 6%

 

[chocolatelover]

Hope this pic helps u to understand this concept.
Good luck.

thank you

 

[The Sarcastic Retard]

https://www.xtremepapers.com/community/threads/9702_w15_qp_22-preparations.42407/page-2#post-940009
H E L P !

 

[ahmedish]

KE because the alpha would be moving (KE = 1/2 mv^2 - if something is moving, it has KE)

charge of electron = 1.6x10^-19
1 M (mega) = 10^6
1MeV = (10^6) x (1.6x10^-19) = 1.6x10^-13
5.3MeV = 5.3 x 1.6x10^-13

http://papers.xtremepapers.com/CIE/...and AS Level/Physics (9702)/9702_w07_qp_2.pdf
4c
why don't we use 2x1.9x10^3 for the force since it acts from both directions? shouldn't we double it? Also whats minimum area and whats maximum area? what exactly is happening here because i dont get it at all. would also like explanation for 4d

 

[ahmedish]

Can someone give me an ideal answer to give in
http://papers.xtremepapers.com/CIE/...nd AS Level/Physics (9702)/9702_s15_qp_22.pdf
4bi ( kinetic model) and here http://papers.xtremepapers.com/CIE/...nd AS Level/Physics (9702)/9702_s13_qp_21.pdf 4b
(same question) please urgent my exam is tomorrow

 

[ahmedish]

http://papers.xtremepapers.com/CIE/...nd AS Level/Physics (9702)/9702_s14_ms_22.pdf
why cant i say interfere in 7a

 

[nehaoscar]

Someone explain this please
the grade thresholds say that the maximum mark is 260 and 130
but then the components add up to 270 and 140 ...
Why do they say it as 260 and 130 then???

 

[ahmedish]

View attachment 57272
Someone explain this please
the grade thresholds say that the maximum mark is 260 and 130
but then the components add up to 270 and 140 ...
Why do they say it as 260 and 130 then???

the practical paper is ratio'd down to 30, so if you get 32/40 in practical, your grade is counted as 24/30

 

[nehaoscar]

the practical paper is ratio'd down to 30, so if you get 32/40 in practical, your grade is counted as 24/30

Ohh ... do you know why they do that?

 

[ahmedish]

Ohh ... do you know why they do that?

I'd guess because practical isn't as important so they picked that, they do it in other subjects as well, even gcses.

 

[nehaoscar]

Ok so the part c is the question
now the mark scheme says:

Now if centripetal force is greater shouldn't the mud be held on the disk?
Is it a typo... should it be centrifugal instead?

 

[nehaoscar]

I'd guess because practical isn't as important so they picked that, they do it in other subjects as well, even gcses.

Oh ok They should just keep it as 40 or make the actual paper out of 30 Haha idk why i don't like this

 

[nehaoscar]

i think you should forget about centrifugal.
don't think it's even in the syllabus.

Yeah it's not in the syllabus but centripetal force keeps an object in circular motion, so if it's greater, the object shouldn't fly off but would be kept in motion right?

 

[ahmedish]

Can someone give me an ideal answer to give in
http://papers.xtremepapers.com/CIE/...nd AS Level/Physics (9702)/9702_s15_qp_22.pdf
4bi ( kinetic model) and here http://papers.xtremepapers.com/CIE/...nd AS Level/Physics (9702)/9702_s13_qp_21.pdf 4b
(same question) please urgent my exam is tomorrow

http://papers.xtremepapers.com/CIE/...nd AS Level/Physics (9702)/9702_s14_ms_22.pdf
why cant i say interfere in 7a

someone answer these please

 

[nehaoscar]

they are different bodies, so the mud would fly off.

I'm sorry but I don't get it
So here's what I think ... please correct me wherever possible
1. The mud is placed on the disc when the disc is stationary
2. The disc starts to move with an increasing angular velocity w (omega)
3. The centripetal force keeps the mud on the disc so it doesn't fly off
4. At the edges the centripetal force is greater than at the center
So I hope these 4 points are correct
Then the centripetal force holds the mud in place so it doesn't fly off right? ...
So if this force is greater, why will the mud fly off when it's role is to hold it in place?

 

[nehaoscar]

Can someone give me an ideal answer to give in
http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Physics (9702)/9702_s15_qp_22.pdf
4bi ( kinetic model) and here http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Physics (9702)/9702_s13_qp_21.pdf 4b
(same question) please urgent my exam is tomorrow

The molecules of the gas are in random motion and are constantly colliding with each other and the walls of the container
When they collide with the walls of the container, there is a change in momentum
The force (pressure) exerted by the molecules is equal to the rate of change of momentum
The average force (pressure) is the sum of all the individual collisions of the molecules with the walls of the container

 

[nehaoscar]

http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Physics (9702)/9702_s14_ms_22.pdf
why cant i say interfere in 7a

I guess because the question asks about interference so you can't use that word in the answer

 

[The Sarcastic Retard]

http://papers.gceguide.com/A Levels/Physics (9702)/9702_s15_qp_22.pdf
Q2 and Q4

 

[awesomaholic101]

http://papers.gceguide.com/A Levels/Physics (9702)/9702_s15_qp_22.pdf
Q2 and Q4

U want soln?
Q4a:

Other subquestions in ms

 

[The Sarcastic Retard]

U want soln?
Q4a:

Other subquestions in ms

Oh sorry, I forgot to mention the subparts of the question. I got this.. I dont know how to write for b and c.