The Physics PHYA2 thread! 5th June 2013

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here are all the 6/8(when including diagram) markers so far:
specimen- double slit experiment
jan 09 - velocity of a ball
jun 09 - measuring an unknown mass
jan 10 - young's modulus
jun 10 - gymnast an energy loss/types of energy
jan 11 - stationary waves
jun 11 - double slits
jan 12 - diffraction grating
jun 12 - determining spring constant
jan 13 - formation of stationary waves (again)

jun 13 ???????????????????????????????????????

Look at individual ones for more info. but i guess it will probs be waves or slits/diffraction grating

Reply 881

StalkeR47

Original post by BenChard

jun10 q3d

Talk about polaroid sunglasses. And they reduce glare from the reflection because they polarise the incident rays. Is that ok? :smile:

Reply 882

x-Sophie-x

Original post by BenChard

jun10 q3d

The question about uses of polarising filter? o.O

Reply 883

x-Sophie-x

Original post by StalkeR47

The area under the curve (is the triangle which is given by a=1/2ab). Your a is the x-axis and b is the y-axis. Or something like that. Just replace the energy stored equation with the area and replace those delta L and K with the a and b. Is that ok? :smile:

Thank you! I completely forgot about that.
Can you simply prove it by using a graph though? :smile:

Reply 884

yorkshire.lad

Original post by x-Sophie-x

I did the same thing as you :L

X and Z are in phase because they are 'doing the same thing at the same time'
X and Y are antiphase because they are doing different things.
This applies because the wave is a stationary wave :')

Aah right cheers, didn't spot that, still quite a terrible question though :X lol.

Reply 885

Raimonduo

Original post by yorkshire.lad

Done all the past papers, this question was the only one really that made no sense at all.

Specification states that we should be able to know if a wave is

180^{o}

\pi

out of phase.I don't think they want you to know how out of phase are. If you are ever faced with a question like this though, it's either in-phase or

180^{o}

\pi

out of phase.

Reply 886

orangutans1995

[QUObecauseorkshire.lad;42967497]Done all the past papers, this question was the only one really that made no sense at all.

The question asked to state the phase relationship between x and y, and x and z, I calculate that X and Y are 135 degrees out of phase, and x and z are 315 degrees out of phase. However the mark scheme for the June 2012 paper states that the phase relationship between x and y is completely out of phase/180 degrees, and between x and z is 360/0/2pi radians completely in phase.

It makes no sense at all? Please help.
Its because its a stationary wave. If two points are on the same side of the stationary wave (x and z) then they are always in phase. If the are on differnt sides, then they are always out of phase. It doesnt matter about the spacing bettween them because its a stationary wave, just which side they ard on.
I hope that makes sense.

Reply 887

StalkeR47

Original post by Edorrans

Yeah thats great thank you! Could you explain what the difference would be between the white light and the red laser in that drawing?

White light is composed of different colours so the interference pattern seen would be a spectrum with the middle maximum to be the white and brightest and further apart fringes to be less bright and colourful (red and blue/violet). With a red light, since red light has the longest wavelength. This about the equation w=D lambda/s. Increasing the lambda (red light) will clearly increase the fringe pattern seen. Is that ok? :smile:

Reply 888

yorkshire.lad

Original post by Raimonduo

Specification states that we should be able to know if a wave is

180^{o}

\pi

out of phase.I don't think they want you to know how out of phase are. If you are ever faced with a question like this though, it's either in-phase or

180^{o}

\pi

out of phase.

Original post by orangutans1995

[QUObecauseorkshire.lad;42967497]Done all the past papers, this question was the only one really that made no sense at all.

Its because its a stationary wave. If two points are on the same side of the stationary wave (x and z) then they are always in phase. If the are on differnt sides, then they are always out of phase. It doesnt matter about the spacing bettween them because its a stationary wave, just which side they ard on.
I hope that makes sense.

Thank you both, if it comes up tomorrow atleast i know now :smile:

Reply 889

sceezy

JAN 2012 question 7b and 7c ???

Reply 890

Raimonduo

Thank you both, if it comes up tomorrow atleast i know now :smile:

Hope it comes up, I love waves.

Reply 891

x-Sophie-x

Original post by yorkshire.lad

Aah right cheers, didn't spot that, still quite a terrible question though :X lol.

I agree. Took me a long while to work out why you dont work out the actual phase difference >.<

Reply 892

RU486

How would I do 6bii on June 12?

Reply 893

StalkeR47

Original post by x-Sophie-x

Thank you! I completely forgot about that.
Can you simply prove it by using a graph though? :smile:

Yep you can. If you have a line drawn, for extension against the force. so, e=1/2 x F x Delta L gives the energy stored in the extension. :smile:

But, I remember this was question on that. They gave you a graph did not they? So you do not need to prove by drawing the graph unless they have not given you and you have a space. :smile:

Reply 894

Substitution

it's 2d not 3d sorry!!

I hate physics!!!

Original post by StalkeR47

Yep you can. If you have a line drawn, for extension against the force. so, e=1/2 x F x Delta L gives the energy stored in the extension. :smile:

But, I remember this was question on that. They gave you a graph did not they? So you do not need to prove by drawing the graph unless they have not given you and you have a space. :smile:

Ooh there's a past question on this already? Didn't realise that, haven't done all the papers :s-smilie:

Reply 897

StalkeR47

Original post by mikey2912

I hate physics!!!

I love physics! Guys!!!!! Thumbs up if you agree with me! :smile:

Reply 898

Raimonduo

Original post by Raimonduo

Hope it comes up, I love waves.

When it says 'the knot becomes motionless', you want to immediately think back to the basics of stationary and progressive waves, and what stationary waves consist of and how they've formed. When it says knot, it implies node, and as the standard definition of a node states: "A node is fixed point in a stationary wave where there is no particle vibrations and the amplitude is 0." Thus, linking it back to the question, it's a simple "how is a stationary wave formed", in the context of a rope.

Hope that helps a little :smile:

Reply 899

Pirateprincess

Original post by SAS18

I agree that one of the wave ones seems like the most likely option. However, it seems that this year the examiners are trying to be creative across all the boards, so thus far I have found that "expect the unexpected" is a phrase to live by (I mean, look at the six-marker for unit 1). SO... the real question is what would you least expect?