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    (Original post by WurfWurf)
    Hope this helps for 5d

    Thanks so much!!!!!!!!!!!!!!!!!!
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    Can someone please explain how amplitude of stationary wave varies but same in progressive wave?
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    (Original post by ryandaniels2015)
    Can someone please explain how amplitude of stationary wave varies but same in progressive wave?
    Is it not because on a stationary wave, two waves superimpose on each other and form nodes and anti nodes based on the wavelength/ frequency.
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    (Original post by WurfWurf)
    Is it not because on a stationary wave, two waves superimpose on each other and form nodes and anti nodes based on the wavelength/ frequency.
    Yes I think that must be it thx
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    (Original post by McDerdactyl)
    My physics teacher gave us sheets last year with what was on every paper (for units 1 and 2) up until 2014 with predictions for what will be on the 2015 paper and it wad quite good tbh! I was going to ask for them again this year but he just left to go and work somewhere else a few weeks ago which is always great this close to exams! I might have to ask another teacher if theres an email i can contact him with to try and get them ahahah if i manage to get them, ill post them up here!
    I am guessing you have had no luck? haha
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    Getting close now, hoping to max out this exam to make an A easier in unit 4 & 5.

    Wondered if anyone could answer a few questions, also if anyone has questions ( diffraction my strong point/or anything feel free to ask, I find it helpful discussing the subject when it gets this close)

    My main question is about stress strain graph questions, when asked to plot the graph once the elastic limit has been reached and stress is periodically decreased. I get that its a straight line back to x axis, and that original length is longer so its in front of the original line. But mark schemes regularly quote a seemingly random limit which your line has to be drawn between ie between 4.44 & 5.44?

    Am i missing something, because it seems like its impossible to predict where the line is supposed to be drawn back to.
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    Also another question regarding materials.

    A question asked which property was a measurement of a components material.

    The options were; breaking stress, stiffness constant, stress, strain and youngs modulus.

    I put stiffness constant and breaking stress as neither required lengths or volumes which would require a particular objects dimensions to be known which wouldnt be specific to a material.

    The answer was breaking stress and youngs modulus, if youngs modulus relies on length and extension and cross sectional area, how is it specific to a material, and how is stiffness constant not correct?
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    (Original post by philo-jitsu)
    Getting close now, hoping to max out this exam to make an A easier in unit 4 & 5.

    Wondered if anyone could answer a few questions, also if anyone has questions ( diffraction my strong point/or anything feel free to ask, I find it helpful discussing the subject when it gets this close)

    My main question is about stress strain graph questions, when asked to plot the graph once the elastic limit has been reached and stress is periodically decreased. I get that its a straight line back to x axis, and that original length is longer so its in front of the original line. But mark schemes regularly quote a seemingly random limit which your line has to be drawn between ie between 4.44 & 5.44?

    Am i missing something, because it seems like its impossible to predict where the line is supposed to be drawn back to.
    Yhh I've seen that before, tbh if you make sure that the line is parallel it should fall into the range they give I think.
    Btw have you noticed how strict the mark scheme has gotten in the more recent papers? I just did the 2015 and I was losing 1/2 marks for the tiniest of things
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    (Original post by philo-jitsu)
    Also another question regarding materials.

    A question asked which property was a measurement of a components material.

    The options were; breaking stress, stiffness constant, stress, strain and youngs modulus.

    I put stiffness constant and breaking stress as neither required lengths or volumes which would require a particular objects dimensions to be known which wouldnt be specific to a material.

    The answer was breaking stress and youngs modulus, if youngs modulus relies on length and extension and cross sectional area, how is it specific to a material, and how is stiffness constant not correct?
    Im not too sure on this one, I got it wrong too
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    (Original post by boyyo)
    Yhh I've seen that before, tbh if you make sure that the line is parallel it should fall into the range they give I think.
    Btw have you noticed how strict the mark scheme has gotten in the more recent papers? I just did the 2015 and I was losing 1/2 marks for the tiniest of things
    Yeah I just did the 15 paper too...been getting full ums and this one dropped me to 110...worrying this close to the exam, there does seem to be a trend of exams getting more and more difficult, or at least the mark scheme.

    Thanks for the response, but when you say parallel, what do you mean? Oh do you mean parallel to the line when it was still obeying hookes law? That makes sense actually, cheers for that!
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    Hi, you mentioned diffraction was ur strong point, the questions on diffraction on the past papers seem much easier to the older questions by topic on physicsandmathstutor, do we need to know it to the detail in the questions by topic?


    (Original post by philo-jitsu)
    Getting close now, hoping to max out this exam to make an A easier in unit 4 & 5.

    Wondered if anyone could answer a few questions, also if anyone has questions ( diffraction my strong point/or anything feel free to ask, I find it helpful discussing the subject when it gets this close)

    My main question is about stress strain graph questions, when asked to plot the graph once the elastic limit has been reached and stress is periodically decreased. I get that its a straight line back to x axis, and that original length is longer so its in front of the original line. But mark schemes regularly quote a seemingly random limit which your line has to be drawn between ie between 4.44 & 5.44?

    Am i missing something, because it seems like its impossible to predict where the line is supposed to be drawn back to.
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    (Original post by ryandaniels2015)
    Hi, you mentioned diffraction was ur strong point, the questions on diffraction on the past papers seem much easier to the older questions by topic on physicsandmathstutor, do we need to know it to the detail in the questions by topic?
    Have you got an example question that you struggle with?...I havent found one Ive had trouble with because I used unit 5's huygnes principle to understand it visually, once you can actually visualise whats going on it makes sense...are you doing turning points in physics for unit 5?
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    Doing medical, e.g. the question i've attached thanks!
    (Original post by philo-jitsu)
    Have you got an example question that you struggle with?...I havent found one Ive had trouble with because I used unit 5's huygnes principle to understand it visually, once you can actually visualise whats going on it makes sense...are you doing turning points in physics for unit 5?
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    (Original post by ryandaniels2015)
    Doing medical, e.g. the question i've attached thanks!
    Yeah they are trickier just had a look, fortunately I dont think they will come up like that as it is the old spec (2004? unless someone knows better)...

    But the question catches people out because its the second order and people are used to this diagram being first order..

    The multiple black lines are the points where radial waves interfere with each other, this happens every, each subsequent interference is 1 wavelength along the lines, which is why the fringe spacing is proportional to wavelength.

    So because its the 2nd order, the dotted line is theta from the plane of the grating, so we can use sin theta equals oppostite over hypotenuse, and the opposite is CE, which we figured out to be 4pi, and the hypotenuse is AC, which we know is 2d, then rearrange for the answer...
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    Yh Thanks seem much harder, however where is the angle when u do opposite over hypotenuse, actually in general when using the equating lambda=dsintheta where is the angle and what is it?


    (Original post by philo-jitsu)
    Yeah they are trickier just had a look, fortunately I dont think they will come up like that as it is the old spec (2004? unless someone knows better)...

    But the question catches people out because its the second order and people are used to this diagram being first order..

    The multiple black lines are the points where radial waves interfere with each other, this happens every, each subsequent interference is 1 wavelength along the lines, which is why the fringe spacing is proportional to wavelength.

    So because its the 2nd order, the dotted line is theta from the plane of the grating, so we can use sin theta equals oppostite over hypotenuse, and the opposite is CE, which we figured out to be 4pi, and the hypotenuse is AC, which we know is 2d, then rearrange for the answer...
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    Didnt answer the first part of question, but as i said above, the dotted line represents the same angle as theta, usually in this triangle formed the opposite to theta = wavelength, but as its for the second order, the angle doubles, so the opposite length (wavelength) doubles, so BD should equal 2pi, and CE should equal 4pi.
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    the angle is the angle between the grating and the dotted line, it is the theta used at the top of the diagram
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    (Original post by philo-jitsu)
    Yeah I just did the 15 paper too...been getting full ums and this one dropped me to 110...worrying this close to the exam, there does seem to be a trend of exams getting more and more difficult, or at least the mark scheme.

    Thanks for the response, but when you say parallel, what do you mean? Oh do you mean parallel to the line when it was still obeying hookes law? That makes sense actually, cheers for that!
    Yep exactly
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    (Original post by philo-jitsu)
    the angle is the angle between the grating and the dotted line, it is the theta used at the top of the diagram
    Thanks but where would it be would it look like this... and if so why?
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    (Original post by ryandaniels2015)
    Thanks but where would it be would it look like this... and if so why?
    Yeah thats right, when you say why...what do you mean? Do you mean why is that angle theta, or why do we use that line?
 
 
 
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