The Physics PHYA2 thread! 5th June 2013

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) Calculating GPE 3.9x10^6 (2)
e) 22.5% (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) An addition as suggested by ThomT94; 'Also, bullet b's distance is not affected by its mass. It's because both accelerate towards the ground at the same rate from the same height, therefore, same time of travel, thus lower horizontal speed causes bullet to travel shorter distance in the given time.'
EDIT: Referring to height being same. OR distance proportional to velocity would also be awarded marks.
-- 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)
f) Plastic deformation means the object won’t return to its original shape/length once the load is removed (1)
g) 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

7) All of the light has the same wavelength (1)
b) Yes, this was the graph of intensity showing the maxima at (roughly) the same height as the central. (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)

I've covered everything except waves, and that shouldn't take very long.

I'm self-teaching and so have been using these resources:

http://www.antonine-education.co.uk/
http://www.thestudentroom.co.uk/showthread.php?t=1821882
http://www.youtube.com/playlist?list=PL5D99A319E129A5B7&feature=plcp

Any others will be greatly appreciated

What do you guys reckon the 6 mark question will be on? I'm dreading it.

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Lol, need to have a good read of that 'ol book sometime soon..

Im making a wild guess that it will have something to do with interference . Me too really, pretty much all the marks i lost on phya1 were worded questions!

Same here, but I also messed up on the electricity questions.

Oh, and why is the physics sub-forum so quiet?

Im making a wild guess that it will have something to do with interference . Me too really, pretty much all the marks i lost on phya1 were worded questions!

Ah great! I hate interference, and anything to with with waves :/

Ah great! I hate interference, and anything to with with waves :/

Yes! Im guessing everyone else loves the mechanics too

Waves is a sour topic here too. Mainly due to a terrible teacher and (in small part) the fact that I haven't really gone over it in detail.

Mechanics is a blessing from above though.

I think pretty much the same.

Does anyone know if we need to know Electron Diffraction in depth?
I've heard different things about the level of detail I need to know.

Don't quote me on this, but the stuff I've had a look through so far doesn't require that much detail in regards to electron diffraction.

Having said that, our exam is going to be fully based on electron diffraction and is going to ask for ridiculous amounts of details.. (Lol AQA y yu no..)

>.<

Isnt it wave diffraction thats in the exam? Like diffraction of light waves

Lol you're right .. Wavefronts and wavelets? That's about the only thing I remember.

Although I tend to think of them as electrons most of the time, partially due to the work we did on the wave-particle duality and because of that Brian Cox lecture about electron diffraction paths (or something..) I'm sure you know the one..

Lol you're right .. Wavefronts and wavelets? That's about the only thing I remember.

Although I tend to think of them as electrons most of the time, partially due to the work we did on the wave-particle duality and because of that Brian Cox lecture about electron diffraction paths (or something..) I'm sure you know the one..