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The Physics PHYA2 thread! 5th June 2013

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Reply 1060
Original post by StalkeR47
That is exactly what I said. ??? I am guessing you are still stuck. Ask again if you are. :smile:


I think I just didn't get your wording (I hate the worded questions on this unit because I don't understand what they want!) until I got the link between the ship's motion and the force. Many thanks for your help :smile:

Do you mind also explaining question 3bii on the Jan 12 paper? I don't understand what the mark scheme expects you to write from the first 2 marking points written (I wrote the stuff below about maximum thrust, resistance increasing with speed and drag eventually equaling thrust).

The mark scheme says "correctly linked" but what are you supposed to write?
Can someone kindly help me on June 2010, q 6di,6dii, &7d
Original post by OliverG
What is the derivation of dsinO=nL


lets say the distance between the centre of 2 adjacent slits is 'd' which can be worked out by doing . so as the wavefront of the source comes in, it diffracts at an angle towards the screen, this can be calculated by using a protractor or a spectrometer. if you get constructive interference you know that the path difference for say the first order is . now using some trig, we know that . sub in and 'd' to give . which gives . now for every maxima or order on the screen, that means you are getting constructive interfence, therefore the path difference with always have to be a whole number (integer) multiple of , so lets call that . therefore you get

on diagram A to C is
(edited 10 years ago)
Reply 1063
can anyone help me with question 7 (b)(ii) on june 2012 ?
Reply 1064
Can anyone tell us how to derive the 2 equations we have to derive?
(edited 10 years ago)
Original post by Qari
Have you got Jan 13 paper?


I have it m8. :smile:
Guys, why is question 7ai on the June 2009 paper worth 4 marks?!
Isn't it just a simple equation that we have to use?
Original post by Claree
I think I just didn't get your wording (I hate the worded questions on this unit because I don't understand what they want!) until I got the link between the ship's motion and the force. Many thanks for your help :smile:

Do you mind also explaining question 3bii on the Jan 12 paper? I don't understand what the mark scheme expects you to write from the first 2 marking points written (I wrote the stuff below about maximum thrust, resistance increasing with speed and drag eventually equaling thrust).

The mark scheme says "correctly linked" but what are you supposed to write?


You can say, streamlined reduces air resistance. :smile:
anyone struggling with any past paper question?
Original post by Nav_Mallhi
Guys, why is question 7ai on the June 2009 paper worth 4 marks?!
Isn't it just a simple equation that we have to use?


yepp easy 4 marks there, just to make sure you did use the dsinθ=nλ dsin\theta = n\lambda for that question yh?
Reply 1070
Original post by Jack93o
anyone struggling with any past paper question?

question 7bii on june 2012 ? :smile:
Original post by Nav_Mallhi
Guys, why is question 7ai on the June 2009 paper worth 4 marks?!
Isn't it just a simple equation that we have to use?


Yes, you have to use dsintheta=n lambda. They said 2nd order (1 mark), correct equation (1 mark), correct calculations (1 mark) answer to 2 or 3 sf only (1 mark). :smile:
Original post by Claree
I think I just didn't get your wording (I hate the worded questions on this unit because I don't understand what they want!) until I got the link between the ship's motion and the force. Many thanks for your help :smile:

Do you mind also explaining question 3bii on the Jan 12 paper? I don't understand what the mark scheme expects you to write from the first 2 marking points written (I wrote the stuff below about maximum thrust, resistance increasing with speed and drag eventually equaling thrust).

The mark scheme says "correctly linked" but what are you supposed to write?


Basically, when it says 'maximum horizontal velocity', it means the point at which the aircraft reaches uniform motion in the horizontal direction (no resultant force acts upon it, newtons first law). Thus, an object with a larger surface area is affected more by air resistance. So it terms of this question, you gotta link in the large surface area of the aircraft, to how air resistance affects it, and so reduces the maximum horizontal velocity it could achieve.
Reply 1073
Original post by StalkeR47
You can say, streamlined reduces air resistance. :smile:


That makes sense, but how does that answer the question? Is it not the fact that the plane is affected by air resistance, rather than what features of the plane affect air resistance, that limits the maximum horizontal velocity? :confused:
Original post by StalkeR47
Ok here is the rule! There will be only one question where they will test you on the significant figures. For the rest of the question, look at the quantity they have given you. EG, 3.2x10^7kg is to 2 sf. This means they are looking for 2 s.f. answers. Is that ok? :smile:

Yeah, I'm okay with the ones where they say "an appropriate number" its just the others, I used to do 3 because of maths but I'll do two now, thank you :smile:
Original post by jasmintaa
wavelength is lambda so its the top one


Apparently you don't use that in this question?


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Original post by masryboy94
yepp easy 4 marks there, just to make sure you did use the dsinθ=nλ dsin\theta = n\lambda for that question yh?


Yep. :smile:
Original post by jasmintaa
Yeah, I'm okay with the ones where they say "an appropriate number" its just the others, I used to do 3 because of maths but I'll do two now, thank you :smile:


haha i agree with you on that one, maths they always want it in 3 s.f. so it does get confusing
Original post by StalkeR47
Yes, you have to use dsintheta=n lambda. They said 2nd order (1 mark), correct equation (1 mark), correct calculations (1 mark) answer to 2 or 3 sf only (1 mark). :smile:


Oh right, thanks! :biggrin:
Original post by Nav_Mallhi
Yep. :smile:


well then lets hope for any easy 4 marker in the exam !!! :eek:

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