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AQA Physics B Unit 4 Discussion (PHB4)

Alright guys, how was it?

Personally I thought it was a fairly easy exam compared to the past papers I've done. Although some of it was a bit iffy.

What'd you think?

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Reply 1

Thoughtless

Thought it was ok - were a couple dodgy bits but overall a nice enough paper

Reply 2

nigel_s

Wasn't too bad. The 6 markers were fairly nice, and that can be a big chunk of marks.

Reply 3

Thoughtless

yeah i was hoping for a resonance and natural frequency bit though coz they are always easy marks

Reply 4

rue the whirl

Good paper, pretty easy. Glad there wasnt any tricky capacitor ones.

Reply 5

02sagooa

i thought is was a confusing paper , like the thermodynamics question the last bit abt the energy i couldnt think of what to do but some1 told me i have to do PdeltaV but oh well, and the momentum question i got confused with working out the speed

Reply 6

memenme_1

02sagooa

yea Because Work Done = Energy transferred....so you just had to multiply the pressure with the difference in volume. Oh and tht momentum...yes....i got a very weird answer for....something 10- something....do you think the speed would be that small for an alpha particle when it rebounds?

Reply 7

Thoughtless

memenme_1

hmm well i got a very high speed :P my value wasnt tjhat much smaller than the original speed.
did you use
m1u1 +m2u2=m1v1+m2v2

Reply 8

alan910_2

memenme_1

I got the speed to be something times 10 to the power 5. Also, it was negative because it is rebounding in the opposite direction.

Reply 9

SoulWind

Not a bad exam at all, I did myself a disservice by not getting the revision in early enough. I ran out of time before I could turn potential C into a B. But that is my fault and my fault alone, the paper was fairly good.

Reply 10

alan910_2

Yeah sounds like most people found it to be an alright exam. The grade boundaries might be quite high! Not good lol

Reply 11

alan910_2

Where all the physicists at? You're surely not revising for biology tomorrow?

And what did people put down as the three terms of the first law of thermodynamics? Was 'Work' zero?

Reply 12

username165864

alan910_2

Where all the physicists at? You're surely not revising for biology tomorrow?

And what did people put down as the three terms of the first law of thermodynamics? Was 'Work' zero?

What I put... So Q and U were equal.
Yes, I am revising for Biology tomorrow soon (as if in 3 hours or so.)

Reply 13

username165864

I thought question 2 was tough, but every other question was fine.

Reply 14

alan910_2

Mathematician!

What I put... So Q and U were equal.
Yes, I am revising for Biology tomorrow soon (as if in 3 hours or so.)

Yeah cool that's what I put. I couldn't think of it being anything else.

Work must of been zero because the net displacement was zero, due to the piston ending back in its starting position.

Reply 15

username165864

alan910_2

Yeah cool that's what I put. I couldn't think of it being anything else.

Work must of been zero because the net displacement was zero, due to the piston ending back in its starting position.

Yeah probably. I made an educated guess there anyway... So it could be wrong. I got most parts wrong on that double side anyway... :shifty:

Reply 16

Jade4666

I thought it was a good paper :-) but I revised capacitance and quantum phenomena last night and not much of it came up :-(
What was hard about question 2? I can't remember the question.

Reply 17

alan910_2

Jade4666

I thought it was a good paper :-) but I revised capacitance and quantum phenomena last night and not much of it came up :-(
What was hard about question 2? I can't remember the question.

Well at least both still came up. Better than not coming up at all.

There wasn't any circular motion! Just realised lol.

Wasn't question 2 the oscillation one with the lorry?

Reply 18

alan910_2

It seems there aren't that many AQA physicists on here. I did a thread like this for chemistry yesterday and loads of people discussed.

Not cool guys.

Reply 19

jas0nuk

Also did this paper today. It wasn't too bad. Surprised about the lack of circular motion!

What did everyone get for the magnitude of the frictional force against the piston in the SHM question?
They said 0.76J of energy is removed in one complete cycle.
I worked it out as

Work done = force * distance
0.76 = force * (0.15 * 4) <-- x4 because in one cycle it goes from +0.15 to 0 to -0.15 back to 0 and then to 0.15 again
.: Force = 1.2N

But other people put different answers. Someone said 9.2N and someone else 2.4N :s-smilie:

The velocity of the alpha particle after hitting the gold nucleus was -1.44 x 10^7 metres per sec (opposite direction but they asked for speed not velocity)