Physics: Post your doubts here!

[Tabi Sheikh]

http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Physics (9702)/9702_s10_qp_21.pdf
Q3 (a), how did they get 'k' as 180 in the energy formula?!

well here they used the formula E=1/2*F*x
they didn't used 1/2*k*x^2...........
they replaced kx with F from F=kx

 

[AhmedMans]

http://papers.xtremepapers.com/CIE/...nd AS Level/Physics (9702)/9702_w12_ms_21.pdf
Last question in the paper, why divide by elementary charge??

 

[sma786]

o

well here they used the formula E=1/2*F*x
they didn't used 1/2*k*x^2...........
they replaced kx with F from F=kx

oh my god lol wow, you're a genuis ! thanks

 

[Shreeram]

man just take any two points on graph and you will calculate the gradient it will e 9.5

thanks man

 

[Manobilly]

http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Physics (9702)/9702_w12_ms_21.pdf
Last question in the paper, why divide by elementary charge??

It is related to the equation Charge=I*T.
Here we have the current and we know the charge for alpha as it has 2 electron so we will multiply it by the electron charge.We need to find number of alpha particles passing thru in one second so we will get it by dividing the current over the charge since we need to find the number in one second not the time.

I hope it is clear

 

[soso247]

PHYSICS AS OCTOBER 2010 PAPER 21 HELP :'(
Hey guys: Can someone please explain to me how to do question 6 especially part b :'( Thank u so much and good luck with your exams

 

[daredevil]

http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Physics (9702)/9702_s09_qp_2.pdf

Both Variants are present... just scroll down and you will find the variant 22 paper

Q 6 b ii) We only use v = d/t only when velocity is constant and acceleration is 0.

the part i.. shows that the acceleration is not zero so velocity can't be constant.. so can't use that fomula.. we will have to use s = ut + 1/2 at^2

since intial speed is zero .. formula becomes s = 1/2 at^2

Q2.. Well even I am not that good in physics to be able to solve this one All I can do is that the time at which it reaches max height is when v = 0 .. so t = 2.4s

o thanku so much
and haha yeah that is the one part i got right too in ques 2

 

[Tkp]

ok

Maximum height means velocity =0 and velocity is 0 at 2.4s
just find the area between this points
.5*9*2.4+.5*-6*(4-2.4)=6
The area under the veloctiy time graph is displacement.
and for the momentum my answer is coming negative
and for the finding out the force f=change in momentum/change in time
weight is the ans frm cii
f=ma and u will get the ans

 

[daredevil]

Maximum height means velocity =0 and velocity is 0 at 2.4s
just find the area between this points
.5*9*2.4+.5*-6*(4-2.4)=6
The area under the veloctiy time graph is displacement.
and for the momentum my answer is coming negative
and for the finding out the force f=change in momentum/change in time
weight is the ans frm cii
f=ma and u will get the ans

thanku so much
and don't worry about the negative moment... due to the difference in directions its allowed in the marking scheme so as far as this question goes you're gud to go

 

[Tkp]

thanku so much
and don't worry about the negative moment... due to the difference in directions its allowed in the marking scheme so as far as this question goes you're gud to go

thnks

 

[Alool]

for the first 1 p=v^2/r(put the value of v and p which is in kw)
fr 2nd 1 when s1 is open and s2 and s3 is closed then the power would be zero due to the open of s1.
when s1 and s2 closed and s3 open then the power would be 1.5 becz due to the close of s2 so the power would be 1.5
when 3 of them are closed then the total power is 3 becz due to the close of s2 we get 1.5 and through s3 its 1.5 so total is 3
when s1 closed and s2 and s3 open then the power would be 0.75
s1 closed s2 open s3 closed,so the power of s3 is 1.5 and due to the open of s2 the power would be 0.75
s0 total power is 2.25

i still didnt understand :'(

 

[hassankhan]

http://papers.xtremepapers.com/CIE/...and AS Level/Physics (9702)/9702_s09_qp_2.pdf
Q1 part b
Q7 part b
variant 21

 

[hassankhan]

http://papers.xtremepapers.com/CIE/...nd AS Level/Physics (9702)/9702_s12_qp_22.pdf
Q2 part c

 

[hassankhan]

http://papers.xtremepapers.com/CIE/...and AS Level/Physics (9702)/9702_s08_qp_2.pdf
Q6 part b

 

[Tkp]

i still didnt understand :'(

i cnt help u thn

 

[sumaiyarox:)]

q 9 o/n 2012 pr 41...help plzzz

 

[gary221]

q 9 o/n 2012 pr 41...help plzzz

d whole ques??

 

[sumaiyarox:)]

d whole ques??

yup plzz..n s11 41 too

 

[syed1995]

thnks

taking ----> as + (The direction of velocity)

Negative moment = the moment is in the opposite direction.. in the <---- direction ..

 

[gary221]

yup plzz..n s11 41 too

w12
9 a) Properties of an ideal op-amp:
i) infinite input resistance/impedance.
ii)zero output resistance/impedance.
iii) infinite open-loop gain
iv) infinite slew rate.

b)graph: square wave.
correct cross-over points where V2 = V1.
amplitude 5 V.
correct polarity (positive at t = 0)


c) R emits for a longer time ---> R emits when the Vout is positive.