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OCR Physics A Depth Unofficial Mark Scheme

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Reply 40
Avatar for dman2607
dman2607
Original post by Parhomus
I don't think so; if you used 0.6 s it would give you an answer of exactly 30ms^-1 and the question asked to show it was around 30ms^-1 not exactly 30.


Well usually they don't mind whether use the original value or your own but 28.1 ms seems a bit off for ocr standards, and they said use the value given and the value they gave us was 0.6.
Original post by chemari1
what did you put for the one about the photoelectric effect?


Don't know if I got this one right aha but Personally, I wrote about how uv Ray's have more energy than visible light and hence they have a larger frequency due to equation e=hf. Also included threshold frequency in there. Then stated that as the electron will have more energy when uv light is used it will have a larger Ke max. Therefore it will have a higher velocity due to half mv2. Which was shown in the results as when velocity was used it moved much quicker, however they phrased it. Again, not sure if this is right, seen other people with different explanations
Original post by dman2607
Well usually they don't mind whether use the original value or your own but 28.1 ms seems a bit off for ocr standards, and they said use the value given and the value they gave us was 0.6.


Hmmm, whatever; I think it's a bit ridiculous the way they asked the questions :P, they weren't hard it's just a bit confusing to choose.
Reply 43
Avatar for dman2607
dman2607
Original post by Parhomus
Hmmm, whatever; I think it's a bit ridiculous the way they asked the questions :P, they weren't hard it's just a bit confusing to choose.

I agree. In past papers they don't mind if you use the original or your own value so here, I don't they will care.
Original post by Harrysomers1
Don't know if I got this one right aha but Personally, I wrote about how uv Ray's have more energy than visible light and hence they have a larger frequency due to equation e=hf. Also included threshold frequency in there. Then stated that as the electron will have more energy when uv light is used it will have a larger Ke max. Therefore it will have a higher velocity due to half mv2. Which was shown in the results as when velocity was used it moved much quicker, however they phrased it. Again, not sure if this is right, seen other people with different explanations


I reffered to the results comparing them once, what do you reckon about that?
Original post by chemari1
I reffered to the results comparing them once, what do you reckon about that?


That should be fine :P
Original post by chemari1
I reffered to the results comparing them once, what do you reckon about that?


Sounds good to me
Original post by Harrysomers1
Sounds good to me
cheers
For the one where you have to work out V I used a maths way would I still get marks for it because it's not in the spec?

I knew Vsin(x) = 6.3 and I knew Vcos(x) = 30 so I divided them and got tan(x) = 0.21, then I worked out the angle x and then substituted it back in to get V as 30.6

Do you think I would get marks lol
Reply 49
Avatar for jackthb
jackthb
4
8a E = 1/2mv^2

eV = 1/2mv^2

2eV = mv^2

sqrt*2eV/m = v

so
2*1.6*10^-19*300/9.11*10-31 = ~ 1*10^7
Reply 50
Avatar for mahmzo
mahmzo
17
Original post by ifailedmygcse
For the one where you have to work out V I used a maths way would I still get marks for it because it's not in the spec?

I knew Vsin(x) = 6.3 and I knew Vcos(x) = 30 so I divided them and got tan(x) = 0.21, then I worked out the angle x and then substituted it back in to get V as 30.6

Do you think I would get marks lol



I did the exact same thinf as you :smile:. Yeah its right. It is logical it makes sense and therefore it will be right. Other people used another method and still got around the same answer
Reply 51
Avatar for dylan1016
dylan1016
OP
6
Original post by mahmzo
I did the exact same thinf as you :smile:. Yeah its right. It is logical it makes sense and therefore it will be right. Other people used another method and still got around the same answer

Yeah I did too but people suggest thats wrong.
Reply 52
Avatar for dylan1016
dylan1016
OP
6
Original post by ifailedmygcse
For the one where you have to work out V I used a maths way would I still get marks for it because it's not in the spec?

I knew Vsin(x) = 6.3 and I knew Vcos(x) = 30 so I divided them and got tan(x) = 0.21, then I worked out the angle x and then substituted it back in to get V as 30.6

Do you think I would get marks lol


I'm sure the horizontal was 30, the vertical was 6.3 and the resultant was 30.6 so 31.
Original post by dylan1016
I'm sure the horizontal was 30, the vertical was 6.3 and the resultant was 30.6 so 31.


Yep, that's correct if you used the values they gave you that they wanted you to show; I just thought that it would be better to use the actual values instead. Surely they should give me the marks D:
5800 for the gradient?? I got 6 :/
I've posted this on another thread but here it is again:

Original post by apixytm
I've posted this on another thread but here it is again:



i did it all those steps but i forgot to right out that KE= 1/2mv^2... how many marks will i lose for this question or will i lose all the marks
Original post by dididid
i did it all those steps but i forgot to right out that KE= 1/2mv^2... how many marks will i lose for this question or will i lose all the marks


You don't necessarily have to explicitly state KE=1/2mv^2 on separate line as long as you plugged it into the first equation you should be fine.
There are more than 1 way to do this question and all will be accredited on the same basis that you reach the final unit answer.
Original post by apixytm
You don't necessarily have to explicitly state KE=1/2mv^2 on separate line as long as you plugged it into the first equation you should be fine.
There are more than 1 way to do this question and all will be accredited on the same basis that you reach the final unit answer.


oh okay thanks... thats a relief lol :smile:
Question 3 was electicity i think.

I cant remember the questions/answers...anybody help??

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