2012 Higher Physics Discussion

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Original post by DragonHeartstring

Can the gain of the op amp be negative..? :L I should know this, I just can't think. I said gain = -Rf/Ri, = -5.6

Would I still get the mark?

I think it would only be negative if it's an Inverting Op Amp, this one was Differential, I got +5.6

Reply 561

tomathon1

Original post by bob169

hope 1 cos, wrote formula down and ohm at the end

i ment you will lose one or a half lol :biggrin:

probably get 1mark

Reply 562

Tycho

Original post by Herzschmerz

c) Krypton (but was unsure)

Largely agree with your answers except this one. The Xenon one had more massive particles and I think this is actually a momentum-style question. More massive particles being propelled at the same velocity will have an equal and opposite force and hence be greater than the engine with the less massive particles.

Reply 563

CraigFrew

Original post by TheZorse94

It's kill ohms and also mA

what?

Reply 564

benten17

What did everyone put down for why the water bath should be filled up to above the stopper. I said to ensure all gas, even the molecules just under the stopper, were at the same temperature

Reply 565

tomathon1

Original post by benten17

What did everyone put down for why the water bath should be filled up to above the stopper. I said to ensure all gas, even the molecules just under the stopper, were at the same temperature

same, to make sure all the gas was at the correct temperature :biggrin:

Reply 566

KierMill1

Original post by tomathon1

Q24.b. Calculate the change in speed of the spacecraft. Is 5.6X10-3 totally wrong?

That's what I got, I did something like F = ma to find a, then a = Delta v / t to find the change in speed

Reply 567

ThomasKTPQ

I said to ensure all of the gas molecules were at the correct pressure? idk.

Reply 568

bob169

21)a) 15.7 but 16km, cos Question is 2 sig fig and bearing 155
ii) s/t=16/1.25=13km/h
b) same as 21)a
c) time = 33/22= 1.5= v=s/t= 16/1.5= 11 km/h
anyone else go these

Reply 569

Herzschmerz

Original post by Herzschmerz

Some of the answers I scribbled down. They're not necessarily right! :tongue:

21a)i) 15.5km at 154 degrees
ii) 12.4kmh-1
b)i) 15.5km at 154 (same as before)
ii) 10.3kmh-1

22a)i) 61.2m
ii) 11.5m (could be 11.3 -can't read my writing) :colondollar:

b) More likely to hit tree b/c vertical velocity would be less so height at the top of it's path would be less.

23a) proof.
ii) 4.23x10^4
b) 5.6x10^-3
c) Krypton (but was unsure)

24a) P/T is a constant/ they are inversely proportional.
b) can't be bothered typing it. :wink:

c) wasn't sure but I said to make the reading on thermometer more accurate.

25a)i) 1.5A
ii) 3V
iii) 13.5W
b)Greater (but not sure)

More:
26a) graph increasing exponentially
b) 6kOhms (wasn't sure)
c) It is less b/c charging time is less.

27a) proof.
b)i) Differential
ii) 5.6
iii) (A) 1.93V
(B) Didn't get. :frown:

28a) 51.4 degrees
b)i) because it refracts along boundary (?)
ii) 48.8 degrees
c) Diagram shows ray totally internally reflected.

29a) Don't remember what I put.
b) 300400
c) Yes.

30a) Resistance decreases
b) Photoconductive
ii) Don't remember my answer.
c) 6.75x10^-6 A (but could well be wrong)

31a) Don't remember answer.
b) Alpha

Feel free to correct me; there's lots I'm unsure about. :smile:

Reply 570

hollieeilloh

Original post by bob169

21)a) 15.7 but 16km, cos Question is 2 sig fig and bearing 155
ii) s/t=16/1.25=13km/h
b) same as 21)a
c) time = 33/22= 1.5= v=s/t= 16/1.5= 11 km/h
anyone else go these

I got these roughly, I kept it at 15.6 so my answers were slightly different but yeah :smile:

Reply 571

bob169

Original post by hollieeilloh

I got these roughly, I kept it at 15.6 so my answers were slightly different but yeah :smile:

do you have to use sig figures cos i get 2 teachers one syas you have to use same as question one says dont use too many total confusion haha

Reply 572

hollieeilloh

Normally when I look at these forums I get different answers but from the looks of things I could be on track for an A, crazy considering I was getting D's 3 months ago :smile:

Reply 573

bob169

Original post by Herzschmerz

More:
26a) graph increasing exponentially
b) 6kOhms (wasn't sure)
c) It is less b/c charging time is less.

27a) proof.
b)i) Differential
ii) 5.6
iii) (A) 1.93V
(B) Didn't get. :frown:

for the critical angle one, to you not have to say it gets refracted at 90 degrees and some are reflected? or just that, got lpha at the end haha was so happy

Reply 574

hollieeilloh

Original post by bob169

do you have to use sig figures cos i get 2 teachers one syas you have to use same as question one says dont use too many total confusion haha

Emmm for most of the questions I did keep to the same amount of significant figures, however for this one I just used 15.6 cause I thought it was more accurate :smile:

I'm really not sure if you lose marks or not though aha, just depends on your marker I guesss!

Reply 575

Tycho

Original post by bob169

for the critical angle one, to you not have to say it gets refracted at 90 degrees and some are reflected? or just that, got lpha at the end haha was so happy