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# OCR Physics A AS-exams today! watch

1. (Original post by friday13th)
Lol, it was the long answer question on motive force

Explain how the tyres make a motive force

How is friction important for acceleration and decelleration

i just didnt know what to write

i drew a diagram of a tyre, with friction doing to the left, and motive force to the right, tyre travelling anti clockwise
oh yeah. im not good at these kinda questions myself - i'm better at calculations

i put something along the lines of...
the engine provides the motive force to the axels of the wheels . the tyres push backwards on the road and the road pushes forwards on the tyres causing the tyre rotate and the car to move. then i drew a diagram

i think i got 3 out of the 5 marks for this question

i dont remember what i wrote for the friction one. i did 2 diagrams with friction acting in the opposite direction to the acceleration.
2. and what did you get for the mass of the water, and the speed of the water?

80, 50.5 something like that anyway.

Also how did you explain Potential energy etc..
i just wrote the equations and said what the letters were
3. (Original post by friday13th)
and what did you get for the mass of the water, and the speed of the water?

80, 50.5 something like that anyway.

Also how did you explain Potential energy etc..
i just wrote the equations and said what the letters were
i dont remember the exact values for the speed of the water but i used mgh = 1/2mv^2 and reaaranged the formula to V = sqaure root of 2gh. i dont think we had to find out the mass of the water, i dont remember that.

for the equations i wrote the full definitions and the equations.

GPE - the energy that an object has due to its position above the Earth
GPE = mgh

KE - the energy that an object has due to its motion
KE = half mv squared

im suprised those where worth 2 marks each. it said explain the quantities so i dont think you should have put the formula down. only if it sed define or something like that but i dunno - i could be wrong.
4. Waves properties was ok i think.

Electrons and Photons was pretty hard. i def. lose 2 marks on the last part of the question on LDR. but at least i answered all the other questions so it shouldnt be too bad.
5. (Original post by hihihihi)
Waves properties was ok i think.

Electrons and Photons was pretty hard. i def. lose 2 marks on the last part of the question on LDR. but at least i answered all the other questions so it shouldnt be too bad.
Ohh, i remember the LDR question. the resistance of the LDR depends on the light intensity falling on it. if look at the diagram carefully, you'll notice that the light source is coming from infront of the fan. when the fan spins the propellas block some of the light that is falling on the LDR so its resistance increases causing the voltage across it to drop. When the propella of the fan is not blocking the light, there is more light falling on the LDR so its reisistance decreases and the voltage across it increases. that's why the graph was a square wave - it shows that the fan was blockin the light then unblocking it and then blockin it again... hope you understand this.
6. (Original post by nofronting)
Ohh, i remember the LDR question.
I bet E+P is easy for you doing A2 electronics eh?
7. (Original post by capslock)
I bet E+P is easy for you doing A2 electronics eh?
You would think so but in A2 Electronics we don't cover that sort of stuff - it's the AS Electronics that helped me with E&P. The A2 modules are Communication Systems and Control Systems.
8. Was so easy.

Only question I didn't get was in the 3rd paper: diplacement against position graph.
9. (Original post by nofronting)
Ohh, i remember the LDR question. the resistance of the LDR depends on the light intensity falling on it. if look at the diagram carefully, you'll notice that the light source is coming from infront of the fan. when the fan spins the propellas block some of the light that is falling on the LDR so its resistance increases causing the voltage across it to drop. When the propella of the fan is not blocking the light, there is more light falling on the LDR so its reisistance decreases and the voltage across it increases. that's why the graph was a square wave - it shows that the fan was blockin the light then unblocking it and then blockin it again... hope you understand this.
yeah i got that. but there was a sub question (2makrs )later on- about calculating resistance of the LDR i think.. or something. i didn't get that.
10. (Original post by TheQueen1986)
Was so easy.

Only question I didn't get was in the 3rd paper: diplacement against position graph.
Initially i copied the first graph but then after i realised that we calculated the wavelength of the wave just before that graph question so it must have been related to the graph question in some way. i think the Y axis was displacement and the X axis was position so you had to draw a wave similar to the 1 in the first graph with an amplitude of 1.4 and a wavelenth of XXXX metres using your own scale.
11. (Original post by hihihihi)
yeah i got that. but there was a sub question (2makrs )later on- about calculating resistance of the LDR i think.. or something. i didn't get that.
oh yeah i used the voltage divider formula for this vout = vin * r2/ r1+r2. i dont remember the question though - was it calculate the voltage accross the resistor?
12. (Original post by nofronting)
Initially i copied the first graph but then after i realised that we calculated the wavelength of the wave just before that graph question so it must have been related to the graph question in some way. i think the Y axis was displacement and the X axis was position so you had to draw a wave similar to the 1 in the first graph with an amplitude of 1.4 and a wavelenth of XXXX metres using your own scale.
Yeah, that question was worded a bit strange...position... that word made me think a bit. I just drew the wave with a wavelength of 3.6m and a amplitude of 1.2mm. Hope that's right! Silly words, grrr!
13. (Original post by ThunderCat8)
Yeah, that question was worded a bit strange...position... that word made me think a bit. I just drew the wave with a wavelength of 3.6m and a amplitude of 1.2mm. Hope that's right! Silly words, grrr!
Did you use V = F lamba to work out the wavelenth coz i got a much bigger wavelength than that! was a 4 digit number.!?

LOL, come to think of it my wavelength was kinda big - what did you get for the frequency?
14. (Original post by friday13th)
i think i got 50.5 for something, and about 80 for the mass of water
Thats what i got... 50.4 for the force of the... youngs modulus question, just ova 80 for the water, the 2nd extension doubled, to 8.4... i got 699mm for that 1st, and id left it at that when 'we' finished, but it turned out to be the year 12s n i had an extra 15 mins to save it surely for the deceleration the wheel continued to move clockwise, just the friction changes so it slows down?! hmm

ova all i think iv improved on my 48/60... which means some extra ums in the easiest paper
15. (Original post by ThunderCat8)
Yeah, that question was worded a bit strange...position... that word made me think a bit. I just drew the wave with a wavelength of 3.6m and a amplitude of 1.2mm. Hope that's right! Silly words, grrr!
yeah i got that. and my frequency was something like 417Hz to 3sig figs, using f=1/T
16. (Original post by hihihihi)
yeah i got that. and my frequency was something like 417Hz to 3sig figs, using f=1/T
i got around 40 hz for some reason. wasnt the scale in millimetres?
17. (Original post by hihihihi)
yeah i got that. and my frequency was something like 417Hz to 3sig figs, using f=1/T
I got the same answer as you. Makes me feel much better when someone gets the same answer as me!

The scale was in mm i believe, I can't really remember tbh with u. I've been revising FFE all afternoon, and I've totally forgotten everything that was in that Wave props paper! Sorry!

How do you revise for Phys Unif Concepts btw? I can't do it!
18. (Original post by ThunderCat8)
I got the same answer as you. Makes me feel much better when someone gets the same answer as me!

The scale was in mm i believe, I can't really remember tbh with u. I've been revising FFE all afternoon, and I've totally forgotten everything that was in that Wave props paper! Sorry!

How do you revise for Phys Unif Concepts btw? I can't do it!
I probably got it wrong then!

I have FFE and UC on Thrusday aswell i havent done any mock papers on the UC paper so i dont know yet!
19. (Original post by friday13th)
Lol, it was the long answer question on motive force

Explain how the tyres make a motive force

How is friction important for acceleration and decelleration

i just didnt know what to write

i drew a diagram of a tyre, with friction doing to the left, and motive force to the right, tyre travelling anti clockwise
I didn't draw any diagrams. I thought I did okay on that question until you mentioned that. There wasn't a space to draw diagrams was there? I hope there wasn't...
20. there was LOTS of space for diagrams.

I got 500 Newtons i think, for the piano youngs modulus!!

50 for the speed of the water question,

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