The Physics PHYA2 thread! 5th June 2013

you had to add 30 (you were given this) and 22 (had to work this out - think there was an isosceles triangle or something) to get the angle of incidence (52)

There was an extra angle on the diagram

so it was actually

Hmm I don't think I really looked for this extra angle

Don't worry I did F=weight*accelleration and wrote down the phases differences for B to C because i didn't bother to read the question

Can someone draw it?

YES.

I also got the question on polarisation wrong and the intensity graph, hopefully 65 is 120ums :/

I think the mechanics was good

Good luck for results

recon about 47, because jan 13 was quite easy, and this was a bit harder, but not too bad

What exactly were you supposed to put for it? I put that the wave can only oscillate in one direction. I wasn't really sure how to explain it though.

What exactly were you supposed to put for it? I put that the wave can only oscillate in one direction. I wasn't really sure how to explain it though.

I think 120 UMS will be 63, so maybe 53 for an A

For both the phase questions I put 90o. Because one was 90 ahead of the first particle and one was 90 behind. Is 90 for both correct or would it have to be 90 and 270?

For both the phase questions I put 90o. Because one was 90 ahead of the first particle and one was 90 behind. Is 90 for both correct or would it have to be 90 and 270?

PHYA2 (Provisional, and very shaky) Mark scheme;

Question 1 – Simple matter of working out forces and that stuff, efficiency question may cause problems though.

1) 6082N, which is 6100 to 2sf (2)
b) 9.5 degrees using arctan of 1000/6000 (2)
c) Acceleration was 9.2ms^-2 (2)
d) Can’t remember what this one was asking but I got 3.9x10^6 (not sure) (2)
e) I got 20.5% but I’m not sure as I’ve heard people give various answers (3)

Question 2 – Fairly straightforward question about projectiles.

2) Time taken was 0.55s (2)
b) The horizontal distance was 248m I think (2)
c) As both bullets have the same mass, S=ut will be smaller for the bullet with the lower horizontal velocity (3?)
-- Can’t remember if there was anything more to this question

Question 3 – Perhaps the best 6 marker they’ve ever given, very straightforward.

3) The ball begins to accelerate with a large acceleration as its weight force is (one of) the only forces acting as it begins to move. The gradient then begins to slowly decrease as the resistive forces begin to balance out the weight force. The ball finally reaches terminal velocity as the resistive forces balance out the weight force. Appropriate reference to Newton’s first law needed. Then the ball remains at that velocity, as there is no external force, give reference to Second Law. (6)
b) Initially a straight line indicating uniform acceleration, then a curve of decreasing gradient ending with the ball at terminal velocity. (3)

Question 4 – A decent question, I guess.

4) Weight of the ball was 0.44N (2sf) using volume of a sphere which is given in the data sheet!!! (4)
b)Hooke’s law states that force applied is proportional to the extension up to the limit of proportionality (2)
c) Gradient was roughly 1150/1100 Nm^-1needed (3)
d) Using the area of a triangle and then counting (roughly) 9 small boxes each of area 0.025 gave 1.08J (3?)
e) Straight line parallel to the first one but not finishing at zero as plastic deformation has occurred (2)
d) Plastic deformation means the object won’t return to its original shape/length once the load is removed (2)
f) Work is less as area under graph is less energy absorbed as heat and in permanent extension (1)

Question 5 – Wasn’t too bad..

5) Two conditions for TIR were an angle greater than the critical angle and moving from a medium of higher refractive index to lower (2)
b) Defining the frequency of a progressive wave. Just explain the equation? (1)
c) Speed of light in the object thing was 1.7x10^8 (2)
d) Proof that the angle was about 31.8 degrees using Snell’s Law
e) Critical angle was 51.1 degrees using 1/sinc (2)
f) Undergoes TIR as (20+31.9) > 51 (2)
e) TIR drawn (not sure about this one and the one above) (1)

Question 6 – Don’t even know, seemed cool..

6) First phase difference was 90 degrees or pi/2. Second was 270 degrees or 3pi/2 (2)
b) Oscillation between maximum and minimum amplitude; i.e moves up and down (2)
c) Polarisation only occurs in transverse waves; mention something about plane of polarisation (2)
d) Define frequency (1)
e) 750m (2)

Question 7 – I may have flopped

7) All of the light has the same wavelength (1)
b) Can’t really remember – According to Frogs491 its ‘Fringes larger so intensity equal’ -- If this is the graph of intensity, then (2)
c) Safety precautions that need to be taken when dealing with laser light can include; wearing reflective glasses; taking care not to shine the light in your eyes (or other people's eyes for that matter); any other sensible answer (2)
e) Last part; white at central maxima and very bright as all of the wavelengths converge at the centre; blue tinge closer to central maxima and red tinge further away; not sure about anything else. (3)

That’s all I can remember guys. I’ve probably omitted quite a few things so if anyone can spot any mistakes, let me know and I’ll make amendments

EDIT: I'm going to start adding in the marks for each question slowly so that should be half done soon. If anyone can remember what the marks are for each question please let me know! Thanks. Done

Got the majority of it now, seems we're one mark over though, so if anyone can spot where the marking is wrong.. Mucho gracias

Still missing some stuff over here guys. Although this post is likely long forgotten now..

I've just about managed to finalise the mark scheme now, but as it says, I think I've given an extra mark to one of the questions somewhere. Again, any corrections are welcome and greatly appreciated.

EDIT: I'm also still clueless as to what the second part of question 7 was, I think it was the intensity graph, but not too sure.

Isn't 4d) 1mark?

It was.

Isn't 4d) 1mark?

It was.

I've just about managed to finalise the mark scheme now, but as it says, I think I've given an extra mark to one of the questions somewhere. Again, any corrections are welcome and greatly appreciated.

EDIT: I'm also still clueless as to what the second part of question 7 was, I think it was the intensity graph, but not too sure.

Oscillates in single plane (1st mark)
and
Transverse (2nd mark)
I'm not sure. I missed out transverse though.