Physics: Post your doubts here!

[Mubbasher Iqbal]

There was this question which asked:
Making reference to the laws of electromagnetic induction, suggest why:
1) an emf is induced in the wire,
2) the emf is alternating.
For the first part obviously we'll use the faraday's law to answer.
But can any one answer the second part WITH REFRENCE TO A LAW?
I mean obviously when a wire is moving up and down, its direction changes and thus (by right hand rule) we know that the direction of induce current will change as well. but how to answer in terms of a law? please help.

 

[Hijab]

Not sure about this one. Here's what the examiner report says:
The answer to this question cannot reliably be obtained by guesswork. Eliminating the pressure at P gives
(h1–h2)ρg = 8000 Pa, so (h1–h2) = 0.060 m. D is the only answer that fits.

Yes D is the answer.... Thankyou very much for your help

 

[biscuitbiscuit]

http://papers.xtremepapers.com/CIE/...and AS Level/Physics (9702)/9702_w04_qp_2.pdf
"Q6(c), i don't get it how p.d. across C would be larger than R?

 

[ashcull14]

ashcull14

thnk u so much

 

[ashcull14]

The calculation shows that it takes 2 ms for one wave to complete its cycle. Now each square on the horizontal axis respresents 0.5ms. Thus dividing 2/0.5, it must take 4 complete squares for the wave to complete on cycle. That happens only in B

thnk u so much

 

[ashcull14]

Please someone tell how to calculate the percentage uncertainty.
Eg Measuring from vernier caliper, my reading is 3.52. How we will calculate the % uncertainty?

your error in 3.52 eg (3.52+-x)..so x/3.52*100=%uncertainity

 

[sara kamal]

http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Physics (9702)/9702_s11_qp_41.pdf

please explain Q10 c 2
and Q9 b2

 

[biscuitbiscuit]

http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Physics (9702)/9702_w04_qp_2.pdf
"Q6(c), i don't get it how p.d. across C would be larger than R?

This question someone!

 

[Mimick]

i can make private videos for you on waves and send it to you. you can ask me questions and doubts.

Thats nice however do u know anyone who teaches in person..I would prefer ur videos as well..Thanks

 

[chocolate_girl]

Mcq 16 and 26
http://papers.xtremepapers.com/CIE/...and AS Level/Physics (9702)/9702_s04_qp_1.pdf

 

[Thought blocker]

Mcq 16 and 26
http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Physics (9702)/9702_s04_qp_1.pdf

16:
B is incorrect because the velocity does not decrease uniformly (it's roughly parabolic), which means height of the ball does not increase uniformly, which means the potential energy of the ball does not increase uniformly (since Ep = mgh and rate of h is not constant).
26:
HOPE IT HELPS

 

[Mohammed salik]

http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Physics (9702)/9702_w12_qp_13.pdf
Q11 and 26 Plz Thanks
Thought blocker

 

[sara kamal]

http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Physics (9702)/9702_w12_qp_13.pdf
Q11 and 26 Plz Thanks
Thought blocker

for 26 answer is B
since 2 x distance between 2 nodes=wavelength
so as in 1m 3nodes are there ,the distance between 2 nodes =1/3=o.333
hence wavelength=2 x o.333=0.666m
so f=330/o.666=495Hz

 

[usama321]

This question someone!

For the same current, there is higher V across C than in the resistor. At 5v or above, even though the current in the resistor will be more than in C, the Voltage across C would be 5v out of the total of 7, thus again making the power dissipated across it higher.

 

[biscuitbiscuit]

For the same current, there is higher V across C than in the resistor. At 5v or above, even though the current in the resistor will be more than in C, the Voltage across C would be 5v out of the total of 7, thus again making the power dissipated across it higher.

View attachment 39428

This is what i don't get, after 5V for the same current resistor R has greater voltage than component C

 

[usama321]

This is what i don't get, after 5V for the same current resistor R has greater voltage than component C

You have got to see the current now, not voltage. The voltage across the two components would be different as they are in series now. in series the current is the same. Therefore, you will have to see the voltages for the same amount of curent

 

[NinjaInPyjamas]

http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Physics (9702)/9702_w12_qp_11.pdf

q23

 

[usama321]

http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Physics (9702)/9702_w12_qp_11.pdf

q23

Total constant of the three forces would be:
For the two above, it would be 2k. Now, add the third one,
1/2k + 1/3k = 5/6k = 6/5k (Just add them together like you do in parallel circuits when they are connected end to end)

W = 6/5k * x
x = W *5/6k = A

 

[usama321]

Suchal Riaz I'd suggest you add this question to your difficult questions thread. I found it difficult.
https://www.xtremepapers.com/community/attachments/screenshot_2014-04-19-11-12-02-png.39406/

 

[NinjaInPyjamas]

Total constant of the three forces would be:
For the two above, it would be 2k. Now, add the third one,
1/2k + 1/3k = 5/6k = 6/5k (Just add them together like you do in parallel circuits when they are connected end to end)

W = 6/5k * x
x = W *5/6k = A

thanks a lot!