Physics: Post your doubts here!

[omg]

see Kr has half life of 3 s.....there are two ways....one that u can set up an equation but thats more error prone so better off stick with the second method.........that after 1st 3 s Kr wd be 1/2.....after another 3 s it wud be 1/4th ......and after another 3 it wud be 1/8th whereas because of comparatively very big half life of Ba.....it wud decay be very small amount so after approx. 9 sec rattio will become 8
@OMG i Wanted to ask about an upper part of this question that why is fission energetically feasible......so ms was saying greater binding energy of products compared with reactants....bt how does it explain the energitcally feasible thing

i didnt get it???? actually i didnt understand the QUestion statement!! pls if u could helpp

 

[leadingguy]

i didnt get it???? actually i didnt understand the QUestion statement!! pls if u could helpp

@ OMG
in the question the time is asked for the ratio of undecayed nuclie of Ba /Kr
we know that the no. of undecayed nuclie could be found out by the formula of N = N0e^-lmda.t
now it is given that the ratio of N(BA)/N(Kr) =8 means that N0e^-lmda(Ba).t /N0e^-lmda(Kr).t = 8

now simplify the equation u will get e^- lmda.t/e^-lmda.t as the N0 is cancelled at both sides and lmda and T both are having different values for Ba and Kr will remain as they are


from the given eq. find the value of lamda of Ba and lamda of Kr. from this frmula [lmda= ln2/t0.5


puit it into the remainng eq. u will get the value of T
this value is the time for the nuclie to come atthe situation where the ratio of BA/Kr is 8






did u gt it??? if nt let me know! i will make it even better and easier

 

[omg]

@ OMG
in the question the time is asked for the ratio of undecayed nuclie of Ba /Kr
we know that the no. of undecayed nuclie could be found out by the formula of N = N0e^-lmda.t
now it is given that the ratio of N(BA)/N(Kr) =8 means that N0e^-lmda(Ba).t /N0e^-lmda(Kr).t = 8

now simplify the equation u will get e^- lmda.t/e^-lmda.t as the N0 is cancelled at both sides and lmda and T both are having different values for Ba and Kr will remain as they are


from the given eq. find the value of lamda of Ba and lamda of Kr. from this frmula [lmda= ln2/t0.5


puit it into the remainng eq. u will get the value of T
this value is the time for the nuclie to come atthe situation where the ratio of BA/Kr is 8






did u gt it??? if nt let me know! i will make it even better and easier[/quote]

thankyou so much
i have one other qs too :/ ?

 

[omg]

http://www.xtremepapers.com/CIE/International A And AS Level/9702 - Physics/9702_s09_qp_4.pdf
qs.9 part (b)

 

[XPFMember]

how will i determine the frequency of unmodulated carrier wave

aoa wr wb!
which year ques is this?

 

[leadingguy]

thankyou so much
i have one other qs too :/ ?

ya sure ask it! see If I could ans

 

[omg]

http://www.xtremepapers.com/CIE/International A And AS Level/9702 - Physics/9702_s09_qp_4.pdf

ya sure ask it! see If I could ans

http://www.xtremepapers.com/CIE/International A And AS Level/9702 - Physics/9702_s09_qp_4.pdf qs.9 part (b)

 

[omg]

can i get nov 2011 papers???

 

[omg]

and i wanted to ask is there any site or sth were i can get the experiment design qs for p5, solved!??

 

[unique840]

http://www.xtremepapers.com/CIE/International A And AS Level/9702 - Physics/9702_s09_qp_4.pdf

http://www.xtremepapers.com/CIE/International A And AS Level/9702 - Physics/9702_s09_qp_4.pdf qs.9 part (b)

the activity A0 is stated with 2% error. we hav to get the time for 10% ka error. means original se 8% error. if original is A0, then after 8% error, it will be 0.92A0. we will consider the expression: A = A0* e^(-lambda*time)
lambda will be 0.693/half life
lambda = 0.693/(5.27*365*24*3600)
A = 0.92 A0
so the equation will be:
0.92A0 = A0 * e^(-lambda*time)
A0 will be cancelled
0.92 = e^ (-lambda*time)
ln (0.92) = -lambda*time

 

[unique840]

Asalam-o-alaikum
Can you please help with these physics paper 1 questions?
Questions 13, 14, 16, 25, and 33. Thank you very very much.
http://www.xtremepapers.com/CIE/International A And AS Level/9702 - Physics/9702_s05_qp_1.pdf

Please help me with these?

13) moments = force*perpendicular distance
5N and 10N force have anticlockwise moments. (5*2) + (10*2) = 30 N
20N force is clockwise. (20*3) = 60N
resultant = 60 - 30
= 30N

 

[unique840]

Asalam-o-alaikum
Can you please help with these physics paper 1 questions?
Questions 13, 14, 16, 25, and 33. Thank you very very much.
http://www.xtremepapers.com/CIE/International A And AS Level/9702 - Physics/9702_s05_qp_1.pdf

Please help me with these?

33) resistance = (resistivity*length)/area
volume is constant. volume = area*length
length is doubled but volume is constant so area must be half.
area = A/2
length = 2l
resistance = (resistivity * 2l) / (A/2)
= (4*resistivity*l) / A
=4R

 

[unique840]

Asalam-o-alaikum
Can you please help with these physics paper 1 questions?
Questions 13, 14, 16, 25, and 33. Thank you very very much.
http://www.xtremepapers.com/CIE/International A And AS Level/9702 - Physics/9702_s05_qp_1.pdf

Please help me with these?

25) intensity = A^2
I = A^2
2I = (A')^2 A' is the new amplitude
replace I with A^2
2 (A^2) = (A')^2
taking square root on both sides
A' = A * square root of 2
ans is B

 

[omg]

the activity A0 is stated with 2% error. we hav to get the time for 10% ka error. means original se 8% error. if original is A0, then after 8% error, it will be 0.92A0. we will consider the expression: A = A0* e^(-lambda*time)
lambda will be 0.693/half life
lambda = 0.693/(5.27*365*24*3600)
A = 0.92 A0
so the equation will be:
0.92A0 = A0 * e^(-lambda*time)
A0 will be cancelled
0.92 = e^ (-lambda*time)
ln (0.92) = -lambda*time

how did v get o.92Ao??

 

[leadingguy]

and i wanted to ask is there any site or sth were i can get the experiment design qs for p5, solved!??

no idont think that therres any site from which u can solved papers p5 apart p5 could only be tackled by practice as itx all abt calculations, measurements readings, callibiraations etc. u need a lot of practice and mark sceeme could assist u as solved ones.

 

[rz123]

13) moments = force*perpendicular distance
5N and 10N force have anticlockwise moments. (5*2) + (10*2) = 30 N
20N force is clockwise. (20*3) = 60N
resultant = 60 - 30
= 30N

can u plz tell me how does the 10 N force has an anticlockwise moment?

 

[leadingguy]

Re: Physics questions? please?

Question 10 Please.

Thanks!

well itx a big question what should I annswer to it??? u can get all the ans from marks scheme. apart if theres is any confusion in understanding any part of the question let me now abt it! what is that u are unable to understand ?? as if only ans is required than u can get it by mark scheme too????

 

[Mustehssun Iqbal]

Asalam-o-alaikum
Can you please help with these physics paper 1 questions?
Questions 13, 14, 16, 25, and 33. Thank you very very much.
http://www.xtremepapers.com/CIE/International A And AS Level/9702 - Physics/9702_s05_qp_1.pdf

Walikum,
I haven't studied the whole course yet, and I can just coordinate with you on Q.14 and 16 for now.
Q.14
You take the "perpendicular" distance from the line of force to the pivot.
The 10 N force produces an anticlockwise moment. The 5N force also produces the same anticlockwise moment and the 20N force produces a clockwise moment about the pivot , P (see diagram).
You can take anticlockwise, or clockwise direction as positive and the other as negative. In this case, let us consider the anticlockwise moment as the positive direction for this question;
Torque = F1.d1 + F2.d2 - F3.d3
Torque = 10(2) + 5(2)-20(3)
Torque=-30N , i.e Torque=30N in the clockwise direction. Ans A
Q.16) P=W/t (Power=work done/Time taken)
m=(y2-y1)/(x2-x1)
m=40-10/3-2
P=30/1
P=30N Ans C
Also edited: The dotted lines in the diagram of Q.14 represent the perpendicular distances from the lines of forces to the pivot , P.

 

[omg]

can smby explain me the derivation of PV=NkT????

 

[leadingguy]

june o9

question 8 prt b please!
jxt let me know that what is being asked in the question. Am unable to pick up the meanings!