Physics: Post your doubts here!

[Arjun Dhanak]

See 9702/22/M/J/10 question 4 c. here's the link:
http://www.xtremepapers.com/papers/...nd AS Level/Physics (9702)/9702_s10_qp_22.pdf
Is "Length= λ/4" always used to find the lowest frequency?
How do we know how many times the A and N are found?
Lastly, how can we know how many times we draw the whole spiral (with antinode at opening and node at piston) in the tube?
Thanks in advance.
BTW, only 4 days to go so GOOD LUCK TO EVERYONE!!

 

[leosco1995]

the new period is 0.25t where t is the old period.. so that means the new wave would occur four times within the old wave.. yeah? cause frequency=1/time period.. so you just draw a wave with the same amplitude but 4 cycles within one wave cycle on fig 6.2... and that would mean that your wave has a quarter of the period of the old wave.

By cycle you mean wavelength right? Does that mean within one wavelength of the old wave, there has to be 4 wavelengths of the new wave? I'm kind of confused.

 

[angelicsuccubus]

http://www.xtremepapers.com/papers/CIE/Cambridge International A and AS Level/Physics (9702)/9702_w02_qp_2.pdf

Help needed in Q1 part c and Q5 part b(i) .... !!

q1 doesn't have a part c and for 5b(i) .. you just make it lag behind 1/3 of half the wavelength. .. cause 60degrees is pi/3 so its should look like..



sorry, shakey hand on the touchpad

 

[angelicsuccubus]

By cycle you mean wavelength right? Does that mean within one wavelength of the old wave, there has to be 4 wavelengths of the new wave? I'm kind of confused.

yeh.. do you want me to draw it?

 

[leosco1995]

yeh.. do you want me to draw it?

Yeah, please. I want to check if I drew it right.

 

[angelicsuccubus]

where did u get 100 squares=0.2cm from

velocity times time.. gives you cm from the graph..

 

[angelicsuccubus]

Yeah, please. I want to check if I drew it right.

eck my hand's so shaky on the touch pad..

 

[Navi Don]

one complete cycle is 360 deg. so half a wave will be 180 deg. if you start second wave at half point of the first one, you create a phse difference of 180. a quarter you get 90 deg. a thisrd of the quarter and you get 30 deg phase difference. If you still don't get it ask me and I will explain with figures.

dono waves k crest our trough ki height mai kb difference aye ga?like konsa factor effect krae ga?

 

[Arjun Dhanak]

http://www.xtremepapers.com/papers/...nd AS Level/Physics (9702)/9702_s10_qp_22.pdf
question 6 d.. can somebody pls explain..
Thanks in advance...

 

[leosco1995]

eck my hand's so shaky on the touch pad..

View attachment 11088

Awesome, thank you so much. ^^

 

[Arjun Dhanak]

See 9702/22/M/J/10 question 4 c. here's the link:
http://www.xtremepapers.com/papers/CIE/Cambridge International A and AS Level/Physics (9702)/9702_s10_qp_22.pdf
Is "Length= λ/4" always used to find the lowest frequency?
How do we know how many times the A and N are found?
Lastly, how can we know how many times we draw the whole spiral (with antinode at opening and node at piston) in the tube?
Thanks in advance

http://www.xtremepapers.com/papers/...nd AS Level/Physics (9702)/9702_s10_qp_22.pdf
question 6 d.. can somebody pls explain..
Thanks in advance...

http://www.xtremepapers.com/papers/...nd AS Level/Physics (9702)/9702_s10_qp_22.pdf
question 7 (b)(ii).. can somebody pls explain..
Thanks in advance...


BTW GOOD LUCK TO EVERYONE!!

 

[shan5674]

http://www.xtremepapers.com/papers/...nd AS Level/Physics (9702)/9702_w09_qp_22.pdf

4C(ii) all 3 parts please?

 

[Unicorn]

it's just 1/2kx^2=1/2mv^2 and the speed used is twice than the speed found in c(i) so.. 16m/s and k is from the beginning 1250N/m and m is 25g and x you're going to get as 72mm

ohh thanks ♥

 

[Most_UniQue]

How many significant figures must by answer be?

Also in one question my answer was 4.82 but in markscheme its 4.8 so do they cut marks?

Please reply ASAP!!!!

 

[Jaf]

q1 doesn't have a part c and for 5b(i) .. you just make it lag behind 1/3 of half the wavelength. .. cause 60degrees is pi/3 so its should look like..

View attachment 11083

sorry, shakey hand on the touchpad

Uh... no. That not how it will be.
1) It lags. That means any particular crest/trough will appear later in time. In your drawing, it appears earlier. Had it been a displacement-distance graph, the sketch would have been correct (almost (see below) ... )
2) Both, can't obviously start from A.

Here's a picture of my drawing:

 

[littlecloud11]

How many significant figures must by answer be?

Also in one question my answer was 4.82 but in markscheme its 4.8 so do they cut marks?

Please reply ASAP!!!!

Keep all the answers you're not sure about to 3.s.f, they can't penalize you for that.

 

[Most_UniQue]

Keep all the answers you're not sure bout to 3.s.f, they can't penalize you for that.

And for my second question which I asked , will they cut the marks? You sure they wont penalize?

 

[Most_UniQue]

They won't cut marks.
Completely sure.

and dude in another question my answer was 7894 but in markscheme its 7900 although i used exact values in my calculation , what about this?

 

[abcde]

http://www.xtremepapers.com/papers/CIE/Cambridge International A and AS Level/Physics (9702)/9702_s11_qp_23.pdf
Q6 c (iv)

How do we make the sketch?

the new period is 0.25t where t is the old period.. so that means the new wave would occur four times within the old wave.. yeah? cause frequency=1/time period.. so you just draw a wave with the same amplitude but 4 cycles within one wave cycle on fig 6.2... and that would mean that your wave has a quarter of the period of the old wave.

AoA! angelicsuccubus: I think you sort of misread the question. The answer requires a sketch of the same stationary wave 0.25 T later. There's no change in period. So the correct sketch would simply be a straight horizontal line (on the dotted line). leosco1995: In case you're confused, check this simulation: http://en.wikipedia.org/wiki/File:Standing_wave.gif
At t = 0s, the graph is as shown in the question
At t= 0.25 T, the graph is a straight horizontal line
At t= 0.5 T, the graph is again sinusoidal with the antinode 'crest' now being the 'trough' while the nodes remain exactly the same.
At t = 0.75 T, the graph is again a straight horizontal line
At t = T, the same graph as the question again.
(This only applies to a stationary wave. A progressive wave sketch is never horizontal at any time.)

 

[littlecloud11]

and dude in another question my answer was 7894 but in markscheme its 7900 although i used exact values in my calculation , what about this?

you should round up the answer to 7890, that's 3s.f. They won't cut marks for this either.
Also, while determining the no. of significant figures, check the data given in the question. You should try to keep your answer to the same no of sig. figs. that corresponds to the lowest no. of significant figures given in the data in the question.