Post by: jyce on November 11, 2015, 09:15:13 pm
I'm doing the paper for my students, so I'm going to update this post as I go through it. So far I've finished the motion section, so you'll find the answers for this section below.
Please note I'm watching TV and eating at the same time and I'm human, so there could most definitely be mistakes. In fact, considering the size of this exam, I'd be surprised if I didn't make mistakes. If you think there's a mistake, just tell me and I'll fix it. I haven't showed working for the calculation questions, but if you'd like working for a particular question just ask.
Motion
1a. 5 m s-1
1b.
Ek initial = 128 J
Ek final = 108 J
Therefore, the collision is inelastic
1c. 40 N s to the left
2a. 2 m s-2
2b. 8 N
3a. The arrow should be from the car to the centre of the circle; it should be labelled 'FR'
3b. 38 N
4a.
- Ftrack on car or Fnormal perpendicular to the track and outwards
- FEarth on car or Fweight of car directly down the page
- FR represented by a horizontal line to the left of the page
4b. 16.7o
5a. 20 m
5b. 24.82 m (the answer is not 25 m)
6a. 16 J
6b. 16 J (I disagree that signs would be needed in 6a and 6b, especially since 6b did not ask for a change in energy)
6c. 2 m s-1
6d. C
I'm not sure how they want you to explain this. I just wrote: 'The velocity is increasing from 0 to 0.4 m and decreasing from 0.4 to 0.8 m'
7a. 3.69 x 104 s
7b. 1.09 x 108 m
7c. Although the astronaut has a mass and is within a gravitational field and therefore has a weight, there is no normal reaction on the astronaut (i.e. they are in free fall). Since the astronaut's sensation of weight is determined by the normal reaction and there is no normal, they would feel weightless.
Electronics and photonics
8a. You should have one resistor in series, and then two in parallel with one another
8b. The voltage drop across R1 = 6 V, and the voltage drop across both R2 and R3 = 3 V
9a. LED; the LED emits light with an intensity that replicates the amplitude variation of the current through it
9b. Photodiode; it causes the amplitude of the current through it to replicate the changes in light intensity from the LED
10a. 15 kilo-ohms
10b. 75 kilo-ohms
11a. 50
11b. Firstly, negative values in the output signal correspond to positive values in the input signal because the amplifier is an inverting one. Secondly, the peaks of the output signal are flattened at +/-8 V because the input signal goes beyond +/-160 mV and the amplifier cannot give the maximum gain beyond this input range.
11c.
- Firstly, the sloped region of the characteristic should have a negative gradient
- The sloped region should end at -160 mV/+8 V and at +160 mV/-8 V
- Your x-axis should be in mV and your y-axis in V
Electric power
12a. 3.2 x 10-3 N upwards
12b. B
12c. 0.256 mV
12d. The student should replace the split-ring commutator with slip rings. Unlike a split-ring commutator, slip rings maintain fixed connections between the coil and the external circuit and therefore do not reverse the direction of the induced current.
13a.
- Between P and Q the flux should be zero
- Between Q and R the flux should:
- increase at a steady rate
- then remain constant
- Between R and T the flux should:
- decrease back to zero steadily over the same rate at which it initially increased
- then remain at zero
13b.
- Between P and Q the emf should be zero
- Between Q and R the emf should:
- instantly rise/drop to a constant value for the same amount of time the flux was increasing
- then drop back to zero when the flux remains constant
- Between R and T the emf should:
- instantly drop/rise to a constant value for the same amount of time the flux is decreasing
- then should go back to and remain at zero
13c. As the loop enters the field, there is an increase in flux through the loop into the page (when viewed from Figure 14b). Lenz's law states that the induced field will oppose this change in flux, meaning the induced field will be out of the page. With the induced field in this direction, the induced current must flow through the ammeter from X to Y.
14a. 25 Hz
14b. 9.55 x 103 V
15.
- There should be one horizontal line through the solenoid with an arrow pointing to the right
- Four lines should loop around the solenoid with arrows pointing to the left
- None of the lines should be touching
16a. 2 A
16b. 10 V
16c. 16 W
16d. 0.2 A
16e. 0.16 W
16f. This model represents how electricity is transmitted from power stations to houses. Since the power demands would be constant and since P = VI, increasing the transmission voltage would reduce the transmission current. Reducing the transmission current reduces power losses, since Ploss = I2R. Specifically in terms of Alan and Becky's model, increasing the transmission voltage by a factor of 10 reduces the transmission current by a factor of 10, which reduces the power losses by a factor of 100.
Light and matter
17a. When the slide is put in place, this point will be a bright band. This is because, at this point, the light from each slit travels the same distance (i.e. the path difference is zero) and therefore constructively interferes at this point.
17b. C
18a. 5 x 1014 Hz (seriously VCAA?)
18b. h = 4 x 10-15 eV (I imagine some variation would be allowed here)
18c. Your graph should be straight over the top of the dotted graph
18d. Your graph should:
- intercept the x-axis at 7.5 x 1014 Hz
- have the same gradient as the dotted line
19a.
En = 2 = 91.91 eV
En = 3 = 108.88 eV
19b. You should have drawn a line downwards from the n = 3 line to the n = 2 line
20a. The photoelectric effect supports light behaving as particles. This effect shows that the energy of light is dependent on frequency and independent of intensity. The particle model correctly predicts these two outcomes while the wave model does not.
20b. When accelerated through an atomic lattice, electrons produce a diffraction pattern. This indicates that electrons must have a wavelength, which is a wave property.
*Keep in mind questions 20a and 20b were only worth 2 marks each*
21a. Electrons have a wavelength. They can only orbit atoms such that their wavelength is a whole number multiple of the orbit's circumference, because otherwise a standing wave will not occur. As electrons can have only particular wavelengths to orbit atoms, they can also have only particular energies.
21b. You should draw two diagrams: one where an electron is orbiting such that its wavelength fits in a whole number of times without overlap, and one where an electron is orbiting such that its wavelength does not fit in a whole number of times with overlap. I imagine you would be expected to annotate each diagram, indicating how the former is a stable, standing wave pattern while the latter will result in destructive interference.
*In regards to question 21, I'm really not sure how the marks will be allocated*
22. 7.29 x 107 m s-1
Detailed study: Sound
1. B 2. C 3. B 4. B 5. A 6. C 7. B 8. D 9. D 10. B 11. D (B?)
Materials - courtesy of ashmitch!
1. A 2. A 3. C 4. B 5. B 6. D 7. B 8. C 9. D 10. C 11. D
HOPE THIS HAS BEEN HELPFUL :) :) :)
And thank you everyone for your input!
EDIT: Note that some changes have be made this morning, specifically to questions 16f and 20b.
I would appreciate some more advice on questions 10 and 11 of sound. There's been very mixed responses to question 10, but for question 11 it seems the answer is D.
Post by: Davos on November 11, 2015, 09:21:06 pm
Post by: jyce on November 11, 2015, 09:33:09 pm
Shouldn't Q4b) be 16.7*
Yes. I just re-did the question and I had entered the equation into my calculator incorrectly the first time.
Fixed.
Post by: dankfrank420 on November 11, 2015, 09:49:36 pm
And for 5b I just got 25m flat?
Other than that all good I think - I put photodiode for the transducer question, mainly because it has a faster response time.
Post by: boingo on November 11, 2015, 09:56:32 pm
For 7b I just did it again and got 1.1 * 10^8?
And for 5b I just got 25m flat?
Other than that all good I think - I put photodiode for the transducer question, mainly because it has a faster response time.
Same for 7b. I got d equals 25, not sure what you mean by flat though.
EDIT: nvm get what you mean by flat.
Post by: schooliskool on November 11, 2015, 09:57:15 pm
For 7b I just did it again and got 1.1 * 10^8?7b) it said 10 hours 15 mins so it was (60x10x60)+(15*60)
And for 5b I just got 25m flat?
Other than that all good I think - I put photodiode for the transducer question, mainly because it has a faster response time.
5b) I remember it was 24.XX
@jyce, cheers for the answers. For 7c, I thought weightlessness only occurs if there is no gravitational force on the astronaut? Isn't it 'apparent weightlessness' for no normal force?
Post by: dankfrank420 on November 11, 2015, 09:57:45 pm
Same for 7b. I got d equals 25, not sure what you mean by flat though.
Ahaha just a turn of phrase.
I mean as in 25 exactly, no decimal places.
Post by: dankfrank420 on November 11, 2015, 09:59:49 pm
7b) it said 10 hours 15 mins so it was (60x10x60)+(15*60)
That's 7a you're talking about.
Post by: jyce on November 11, 2015, 10:00:39 pm
I'll have a look at the mistakes you're indicating in 10 minutes or so once I've finished electric power.
@schooliskool, question 7c asked if the astronaut would feel weightless, not if he was actually weightless.
Post by: jyce on November 11, 2015, 10:03:43 pm
Post by: schooliskool on November 11, 2015, 10:04:59 pm
Hi guys,Ah rip. Cheers
I'll have a look at the mistakes you're indicating in 10 minutes or so once I've finished electric power.
@schooliskool, question 7c asked if the astronaut would feel weightless, not if he was actually weightless.
For 10b, maybe I got it wrong, the question what value of R should be used for a 10V drop at the thermistor (or w/e it was), and it was 60V so I had R=50k so 50v would be there and 10v at the thermistor, did I miss something? ;d
That's 7a you're talking about.Oh my bad man, I actually got 1.08 x 10^8 for 7b lol
Post by: jyce on November 11, 2015, 10:08:11 pm
Ah rip. Cheers
For 10b, maybe I got it wrong, the question what value of R should be used for a 10V drop at the thermistor (or w/e it was), and it was 60V so I had R=50k so 50v would be there and 10v at the thermistor, did I miss something? ;d
Resistor R had a voltage drop x5 greater than the LDR and therefore had a resistance x5 greater. 15 x 5 = 75 kilo-ohms.
Post by: schooliskool on November 11, 2015, 10:10:31 pm
Resistor R had a voltage drop x5 greater than the LDR and therefore had a resistance x5 greater. 15 x 5 = 75 kilo-ohms.Oh ok, I don't think I even read the question haha. Cheers for posting the answers btw.
Post by: sprout on November 11, 2015, 10:31:13 pm
Post by: boingo on November 11, 2015, 10:32:38 pm
For 13a of electric power, I had the flux decreasing after R bc before then the coil is completely inside the magnetic field still. idk hahaha
Yes same! Lol was too scared to say because I was pretty sure it was wrong. Maybe not :)
Post by: yeahm8 on November 11, 2015, 10:33:01 pm
For 13a of electric power, I had the flux decreasing after R bc before then the coil is completely inside the magnetic field still. idk hahahai had this too?
Post by: sharans on November 11, 2015, 10:36:20 pm
i had this too?
Same here, because the question clearly said "experienced by the front end of the loop" or something along those lines
Post by: sprout on November 11, 2015, 10:37:24 pm
Yes same! Lol was too scared to say because I was pretty sure it was wrong. Maybe not :)
well we can lose 2 marks together if it's wrong lmao
Post by: jyce on November 11, 2015, 10:39:24 pm
Post by: Davos on November 11, 2015, 10:40:12 pm
Post by: dankfrank420 on November 11, 2015, 10:40:28 pm
Excuse the terrible ms paint skills ahaha
Post by: sprout on November 11, 2015, 10:43:16 pm
If I recall correctly shouldn't one of the multichoice questions in electric power be A (the one with the current or voltage graph when the rotor is turned by hand because if it is rotated by hand isn't it AC?
nah bc a commutator is attached, so AC is converted to DC
Post by: jyce on November 11, 2015, 10:44:50 pm
Anyone get this for the graphs?
Excuse the terrible ms paint skills ahaha
That's incorrect: within the first segment of the graph none of the loop has yet to enter the magnetic field, so the flux is zero for that segment.
Post by: dankfrank420 on November 11, 2015, 10:45:26 pm
That's incorrect: within the first segment of the graph none of the loop has yet to enter the magnetic field, so the flux is zero for that segment.
Is any of it correct?
Post by: Davos on November 11, 2015, 10:45:41 pm
nah bc a commutator is attached, so AC is converted to DC
SHIT!! was that a 1 mark question or 2 mark question?
Post by: dankfrank420 on November 11, 2015, 10:50:47 pm
B
C
B
B
A
C
B
D
D
B
B
Post by: jyce on November 11, 2015, 10:51:08 pm
Is any of it correct?
I'm guessing you'd only lose 1 mark out of 4.
Post by: sprout on November 11, 2015, 10:51:23 pm
SHIT!! was that a 1 mark question or 2 mark question?pretty sure it was just 1 mark, so all g
Post by: jyce on November 11, 2015, 10:51:38 pm
Did anyone get this for sound?
B
C
B
B
A
C
B
D
D
B
B
I can confirm shortly. :)
Post by: dankfrank420 on November 11, 2015, 10:52:40 pm
I can confirm shortly. :)
Cheers mate
Post by: GeniDoi on November 11, 2015, 10:54:21 pm
Post by: odeaa on November 11, 2015, 10:58:14 pm
It's a photo diode as an LDR isn't a transducer but rather just a resistor. A photo diode actually produces a time-varying electrical current from the light energy that is incident upon it, which the amplifier boosts up. I think the amplifier is the key herePhew
Post by: jyce on November 11, 2015, 10:59:03 pm
Post by: GeniDoi on November 11, 2015, 11:06:54 pm
I'm fairly confident an LDR is also a transducer. When the intensity of light on it changes, its resistance changes and so current changes.
The LDR wastes energy by converting some to heat based on light intensity and this produces a time varying voltage. For this to work, there needs to be a power supply to supply power for it to waste. You can't have a resistor connected to an unpowered circut - it won't produce a time varying voltage because there is no voltage for it to alter, by the definition of an unpowered circut.
There is no indication in the diagram that a power supply exists in the demodulating circuit. Moreover, an amplifier in such a circut would be illogical at best as the power supply should be supplying all of the power to the loudspeaker for it to function. The only way that it makes sense is if a photo diode is producing a very small time varying current which the amplifier amplifies.
Occam's razor...
Post by: jyce on November 11, 2015, 11:10:24 pm
The LDR wastes energy by converting some to heat based on light intensity and this produces a time varying voltage. For this to work, there needs to be a power supply to supply power for it to waste. You can't have a resistor connected to an unpowered circut - it won't produce a time varying voltage because there is no voltage for it to alter, by the definition of an unpowered circut.
There is no indication in the diagram that a power supply exists in the demodulating circuit. Moreover, an amplifier in such a circut would be illogical at best as the power supply should be supplying all of the power to the loudspeaker for it to function. The only way that it makes sense is if a photo diode is producing a very small time varying current which the amplifier amplifiers.
Occam's razor...
Sure. I'll change it.
Post by: dankfrank420 on November 11, 2015, 11:12:46 pm
Shouldn't the answer be C?
More diffraction, and since the ratio of lamba/s must be greater then s must be a smaller number?
Also I got the same answer for the last question 7.3*10^7
Post by: Davos on November 11, 2015, 11:13:14 pm
Re: 17b
Shouldn't the answer be C?
More diffraction, and since the ratio of lamba/s must be greater then s must be a smaller number?
Also I got the same answer for the last question 7.3*10^7
agreed
Post by: yeahm8 on November 11, 2015, 11:13:54 pm
Post by: jyce on November 11, 2015, 11:15:24 pm
20b. What evidence do we have that electrons behave like waves...
Ugh. Okay I'll fix that.
Post by: GeniDoi on November 11, 2015, 11:17:32 pm
Ugh. Okay I'll fix that. Surely that's a repeat of Question 21a? :o
I'm pretty sure for 21a you could also alternatively mention a modified double slit experiment firing electrons rather than photons since electrons fired through the two slits produce an interference pattern that is a property of waves.
Post by: yeahm8 on November 11, 2015, 11:17:47 pm
Ugh. Okay I'll fix that.yep pretty much, also there was a multitude of things we could have spoken about for 20a correct? not just photoelectric effect?
Post by: jyce on November 11, 2015, 11:20:29 pm
yep pretty much, also there was a multitude of things we could have spoken about for 20a correct? not just photoelectric effect?
True, although the photoelectric effect is really the only piece of evidence within the VCE Physics course.
Post by: jyce on November 11, 2015, 11:20:54 pm
I'm pretty sure for 21a you could also alternatively mention a modified double slit experiment firing electrons rather than photons since electrons fired through the two slits produce an interference pattern that is a property of waves.
Yes, but this is not on the study design.
Post by: GeniDoi on November 11, 2015, 11:24:57 pm
Yes, but this is not on the study design.
But you could have used it and still gotten marks?
Post by: jyce on November 11, 2015, 11:25:41 pm
But you could have used it and still gotten marks?
Yes, but I'm not going to put it in the suggested solutions is all. :)
I think you meant question 20a, and not 21a by the way.
Post by: yeahm8 on November 11, 2015, 11:27:48 pm
Post by: dave101 on November 11, 2015, 11:35:39 pm
Anyway I calculated my percentage to be 85.3%. Btw im in year 11 doing physics 3/4. What study score do you reckon that would be?
Post by: dankfrank420 on November 11, 2015, 11:37:54 pm
I just finished marking the exam myself. I thought it wasn't the hardest exam, but I made so many stupid mistakes mainly because I'm that careless >:( >:( >:(
Anyway I calculated my percentage to be 85.3%. Btw im in year 11 doing physics 3/4. What study score do you reckon that would be?
Just on 40 imo.
Post by: jyce on November 11, 2015, 11:38:40 pm
Just on 40 imo.
Agreed.
Keep in mind these are only *suggested* solutions.
Post by: sharans on November 11, 2015, 11:42:07 pm
B
C
B
B
A
C
B
D
D
B
D.
Not too sure about question 11 though, some of my mates said it was B but others said it was D
Post by: dave101 on November 11, 2015, 11:43:03 pm
Just on 40 imo.
I'd take 40 any day. This year's exam feels a bit more simpler than previous years and students might do better on this year's exam so the average could be pretty high. I'm not too sure. But yeah
Post by: jyce on November 11, 2015, 11:44:09 pm
What I got for sound
B
C
B
B
A
C
B
D
D
B
D.
Not too sure if question 11 though, some of my mates said it was B and other said it was d
I thought D myself, but wasn't sure so went with dankfrank420's answer. I'll put D on there as well.
Post by: Davos on November 11, 2015, 11:46:24 pm
Re: 17b
Shouldn't the answer be C?
More diffraction, and since the ratio of lamba/s must be greater then s must be a smaller number?
Also I got the same answer for the last question 7.3*10^7
JYCE, thank you very much for your services. One last thing, Isn't this correct?
Post by: jyce on November 11, 2015, 11:48:17 pm
JYCE, thank you very much for your services. One last thing, Isn't this correct?
I'm going off the fact that the band separation is proportional to (wavelength x slit separation)/slit-screen separation
ERR never-mind. I mucked up the relationship. You're correct!!
Post by: sprout on November 11, 2015, 11:51:26 pm
Post by: jyce on November 11, 2015, 11:52:32 pm
I wrote about how atoms only absorb discrete amounts of energy as proof for wave properties of electrons.. Would that be alright or nah?
Assuming you explained it properly, that's fine.
Post by: GeniDoi on November 11, 2015, 11:58:31 pm
How many marks lost for the banked angle question if I used the 2m/s value?
Post by: jyce on November 11, 2015, 11:58:54 pm
That bloody banked angle question is so nasty... why would they mention 2m/s and then later change it to a 3m/s??? WTF is the point of that... urgh
How many marks lost for the banked angle question if I used the 2m/s value?
1. Although I suspect it's a mistake in which case they'll give you full marks. If it wasn't a mistake that's just plain cruel and unnecessary.
Post by: ashmitch on November 12, 2015, 12:00:12 am
AAC BBD BCD CD
I've had a few other pretty strong students agree with me but if some are still wrong I'm sorry.
Hope you all went well today & Thanks for posting these solutions.
One last thing, what mark do you think you'll need for an A+ on this paper? , last years was 128, do you think this year is around the same? I think i got somewhere between 133-137 based on these solutions & i'm praying that will get me in the 40's ahahaha
Post by: stockstamp on November 12, 2015, 12:02:55 am
Also for sound, couldn't the answer to question 10 be A? Because while their diffraction would be different, the ratio of wavelength/width of aperture is still below one, so each would experience very minimal diffraction.
Also missed the speed change on the banked curve >:( goodbye 40
Post by: jyce on November 12, 2015, 12:03:21 am
Pretty sure Structures & Materials Multiple Choice were;
AAC BBD BCD CD
I've had a few other pretty strong students agree with me but if some are still wrong I'm sorry.
Hope you all went well today & Thanks for posting these solutions.
One last thing, what mark do you think you'll need for an A+ on this paper? , last years was 128, do you think this year is around the same? I think i got somewhere between 133-137 based on these solutions & i'm praying that will get me in the 40's ahahaha
Thanks. I'll put those answers up.
And that score will definitely net you above a 40. Well done!
Post by: ashmitch on November 12, 2015, 12:08:01 am
Thanks. I'll put those answers up.Oh thank god, i think i might've screwed my chances of getting a 40 in Methods after that exam 2 and definitely screwed it for Spec too after monday's exam, so hopefully Physics pulls through & saves my ATAR
And that score will definitely net you above a 40. Well done!
Post by: dave101 on November 12, 2015, 12:09:10 am
Pretty sure Structures & Materials Multiple Choice were;
AAC BBD BCD CD
I've had a few other pretty strong students agree with me but if some are still wrong I'm sorry.
Hope you all went well today & Thanks for posting these solutions.
One last thing, what mark do you think you'll need for an A+ on this paper? , last years was 128, do you think this year is around the same? I think i got somewhere between 133-137 based on these solutions & i'm praying that will get me in the 40's ahahaha
I'm pretty confident that'll get you over 40. Nice stuff. I got 128/150 which was last years exact 40 raw. But this years exam seems much more doable and kids are saying its more easier which I assume is probs true. I hope mine would at least get me a 40 hahah
Post by: ashmitch on November 12, 2015, 12:11:25 am
I'm pretty confident that'll get you over 40. Nice stuff. I got 128/150 which was last years exact 40 raw. But this years exam seems much more doable and kids are saying its more easier which I assume is probs true. I hope mine would at least get me a 40 hahahI hope yours pulls 40 Raw too, because then mine will pull a bit above 40 Raw ;)
Nah but seriously good luck man & hopefully it all goes well when it comes to results day.
Post by: ashmitch on November 12, 2015, 12:18:00 am
Thanks. I'll put those answers up.Only thing i'm a little worried about was my SAC scores, i was only about an A for both semesters judging by last years distributions :/ So hopefully my exam score is good enough to keep me in the A+, i think we had a fairly good class too and the highest score on SAC's in the class was only 88% but we were all smashing exam papers & getting pretty good marks, so maybe our SAC's were just a bit too hard, HOPEFULLY they were too hard and that A of mine becomes an A+ haha
And that score will definitely net you above a 40. Well done!
Post by: Davos on November 12, 2015, 12:18:16 am
Post by: jyce on November 12, 2015, 12:28:11 am
Thoughts on what SS a 140/150 could deliver?
45+ I'm guessing
Post by: menja12 on November 12, 2015, 02:39:02 am
Sound question 10d? Because lambda is 0.1m at 3000hz, there is no single slit interference pattern and hence no hard edge.
Question 11 is d. No rooms are smaller than 0.1m so b is not even reasonable. Since sound bounces in room there is no single slit destructive interference to create the hard edge. So instead is the blurry edge.
Single slit interference patterns are not on course but the effect of waves in gaps is...
Post by: Toddman on November 12, 2015, 07:45:38 am
Post by: jyce on November 12, 2015, 09:11:21 am
For 26b I talked about the standing wave nature of electrons around a nucleus which is very differend from what you had, is that okay??
I'm assuming you mean 20b, and yes that's fine. There were multiple answers you could have had for both 20a and 20b.
Post by: jyce on November 12, 2015, 09:15:38 am
Q16f is worth 4 marks. It asked for the power losses to be related back to alan and Becky's model. Ie to mention that the factor 10 reduced power loss by factor 100
Sound question 10d? Because lambda is 0.1m at 3000hz, there is no single slit interference pattern and hence no hard edge.
Question 11 is d. No rooms are smaller than 0.1m so b is not even reasonable. Since sound bounces in room there is no single slit destructive interference to create the hard edge. So instead is the blurry edge.
Single slit interference patterns are not on course but the effect of waves in gaps is...
Yes, I'll fix 16f. Good point.
In regards to question 10 of sound, I remain convinced it's B and I've had people saying A and now your saying D. Until I get conclusive support for one answer, I will not be changing it.
And personally I think question 11 of sound is 'D' as well, but we've had some disagreement so both answers have remained.
Post by: shadowhunterqwer on November 12, 2015, 09:35:52 am
Post by: jyce on November 12, 2015, 09:39:51 am
quick question will i be penalised for sig figs? (unlike methods/spesh, phys didnt specify how many decimal places they wanted)
No, unless you gave your answers to such a small number of significant figures that they are quite rounded from the true value.
Post by: Orson on November 12, 2015, 09:49:08 am
@jyce, cheers for the answers. For 7c, I thought weightlessness only occurs if there is no gravitational force on the astronaut? Isn't it 'apparent weightlessness' for no normal force?
Yeah dude. I copied that from the VCAA solutions onto my cheat sheet, so it can't be wrong. Your answer is fine.
Post by: jyce on November 12, 2015, 09:51:19 am
Yeah dude. I copied that from the VCAA solutions onto my cheat sheet, so it can't be wrong. Your answer is fine.
He's answer is not fine if he simply said that the astronaut has a weight. Yes, the astronaut has a weight but the question asked about whether the astronaut feels as if they have a weight; hence, discussion of the absence of a normal reaction was required.
Post by: Orson on November 12, 2015, 10:01:47 am
He's answer is not fine if he simply said that the astronaut has a weight. Yes, the astronaut has a weight but the question asked about whether the astronaut feels as if they have a weight; hence, discussion of the absence of a normal reaction was required.
You mean free fall? Yeah, the dude in the spaceship has no reaction force, thus he is in free fall.
Cheers for doing this!
Post by: dimitrigots on November 12, 2015, 11:05:18 am
Post by: Davos on November 12, 2015, 11:07:37 am
7a) 3.7x10^4 s
7b) 1.1x10^8 m
14b) 9546 V
19a) 91.9 ev and 108.9 ev
Post by: jyce on November 12, 2015, 11:12:13 am
Are these answers ok?
7a) 3.7x10^4 s
7b) 1.1x10^8 m
14b) 9546 V
19a) 91.9 ev and 108.9 ev
Yes.
Post by: jyce on November 12, 2015, 11:12:58 am
unsure of the exact questions, but materials and structures detailed study, I think question9, with the hanging mass and the cables, it asked which components were in tension or compression. I remember specifically putting the option with all 3 in tension, casue that was the only option that allowed the forces to cancel out and provide a net force of zero. unsure if that's the answer you've picked. any feedback?
Sorry, I didn't do the materials answers myself, so I wouldn't know. Hopefully someone that did materials can let you know. :)
Post by: ClivePalmer on November 12, 2015, 11:14:53 am
Cheers
Post by: odeaa on November 12, 2015, 11:15:12 am
unsure of the exact questions, but materials and structures detailed study, I think question9, with the hanging mass and the cables, it asked which components were in tension or compression. I remember specifically putting the option with all 3 in tension, casue that was the only option that allowed the forces to cancel out and provide a net force of zero. unsure if that's the answer you've picked. any feedback?
the tension forces would pull inwards, so the top would have to be in compression
Post by: ClivePalmer on November 12, 2015, 11:16:55 am
Post by: dimitrigots on November 12, 2015, 11:21:25 am
the tension forces would pull inwards, so the top would have to be in compression
if the tension forces pulled inwards, wouldn't the beam pull outwards to balance these forces though?
oh well, 2 marks gone, not bad, haha
Post by: bobisnotmyname on November 12, 2015, 11:51:22 am
Post by: dimitrigots on November 12, 2015, 11:58:50 am
What do you guys think about question 16 c with the power loss question. Is it me or do you think 3 marks is way to much for that question?
Routine power loss questions, I'm just happy for the 3 easy marks. think I got 16w
Post by: turtleman on November 12, 2015, 12:35:37 pm
Post by: jyce on November 12, 2015, 12:44:56 pm
What do you guys reckon the percentage for the exam is for a 40 raw? ;)
Around 85%.
Post by: Xx_Impulse_xX on November 12, 2015, 02:15:17 pm
Post by: doolster on November 12, 2015, 03:47:42 pm
I taught Structures and Materials and those solutions are right.
Nasty how they change the speed in 4b. Also big difference between V and v as far as synchrotron formulas go.
Post by: stockstamp on November 12, 2015, 05:43:22 pm
If the radius and mass are constant n a motion, design speed (ie when friction is effectively 0) can only occur at a single speed.
In part a) the question says 'The angle of the bank is such that there is no sideways frictional forces', and part b) asks you to calculate the speed 'with no sideways friction'. Hence they must be the same speed - Surely! It's impossible to have to difference speeds if all other variables are constant.
Also is it possible that the answer to question 10 of Sound is a? Although the two frequencies are quite different, the wavelength/aperture ratio is far below 1 for both, therefore neither would experience significant diffraction, and the edge of the pattern would still be 'approximately' 1.5m off the centre line. That's what I assumed anyway. Anyone have any thought? Or can someone explain why I am wrong?
Post by: jyce on November 12, 2015, 05:55:23 pm
Would anyone else agree that question 4 must be a mistake?
If the radius and mass are constant n a motion, design speed (ie when friction is effectively 0) can only occur at a single speed.
In part a) the question says 'The angle of the bank is such that there is no sideways frictional forces', and part b) asks you to calculate the speed 'with no sideways friction'. Hence they must be the same speed - Surely! It's impossible to have to difference speeds if all other variables are constant.
Also is it possible that the answer to question 10 of Sound is a? Although the two frequencies are quite different, the wavelength/aperture ratio is far below 1 for both, therefore neither would experience significant diffraction, and the edge of the pattern would still be 'approximately' 1.5m off the centre line. That's what I assumed anyway. Anyone have any thought? Or can someone explain why I am wrong?
Yes, I believe that change in speed was a mistake; nevertheless, the suggested answer is given for 3 m s-1.
In regards to question 10 of sound, I've now had 2 people for A, 2 for B and 1 for D. Until I get more conclusive support for one answer, it'll remain as B.
Post by: Orson on November 12, 2015, 05:58:46 pm
Would anyone else agree that question 4 must be a mistake?
It would be nice if you were right...
Expected Raw Study Score for getting somewhere between 140 to 142 out of 150?
45 easy...
Routine power loss questions, I'm just happy for the 3 easy marks. think I got 16w
Yeap. Same. Did you get 0.2A for the current?
Are these answers ok?
7a) 3.7x10^4 s
7b) 1.1x10^8 m
14b) 9546 V
19a) 91.9 ev and 108.9 ev
Yay...I got something right!
Post by: ashmitch on November 12, 2015, 06:11:04 pm
if the tension forces pulled inwards, wouldn't the beam pull outwards to balance these forces though?
oh well, 2 marks gone, not bad, haha
Pretty sure between points M & N it is definitely Compression, I think outside the points M & N there would be more tension, so the beam as a whole is under both compression & tension, but it asked specifically between M & N so i'm pretty confident it's compression.
Post by: dimitrigots on November 12, 2015, 10:35:19 pm
Post by: GeniDoi on November 12, 2015, 10:41:35 pm
Yes, I believe that change in speed was a mistake; nevertheless, the suggested answer is given for 3 m s-1.
In regards to question 10 of sound, I've now had 2 people for A, 2 for B and 1 for D. Until I get more conclusive support for one answer, it'll remain as B.
Wow... is it actually possible we may have on our hands the first cancelled physics question (ie everyone gets a mark)?
Because surely they can't accept both using 2m/s and 3m/s as valid solutions.
Post by: GeniDoi on November 12, 2015, 10:42:57 pm
energy level question in the atom, people saying 108.8 and 91.9, vcaa would surely accept 109 and 92 as answers wouldn't they? This isn't chem with sig figs
Yeah, they would accept both those.
Post by: bobisnotmyname on November 12, 2015, 11:26:12 pm
Wow... is it actually possible we may have on our hands the first cancelled physics question (ie everyone gets a mark)?I don't think they would cancel the question. Thinking about it now, I think it may have been done so deliberately just to really separate the state. Stupid, but I guess that's the way it is.
Because surely they can't accept both using 2m/s and 3m/s as valid solutions.
Post by: GeniDoi on November 13, 2015, 08:38:53 am
I don't think they would cancel the question. Thinking about it now, I think it may have been done so deliberately just to really separate the state. Stupid, but I guess that's the way it is.
Being good at physics =/= being able to notice every nook and cranny of every page on an 80 page paper in 2 and a half hours for fucks sake. Bloody vcaa should leave that shit for Concentration Studies 3/4
Post by: odeaa on November 13, 2015, 11:17:47 am
Being good at physics =/= being able to notice every nook and cranny of every page on an 80 page paper in 2 and a half hours for fucks sake. Bloody vcaa should leave that shit for Concentration Studies 3/4Amen, how does it prove anything if we noticed a slight change or not. Should be about separating people based on knowledge, not detail analysis
Post by: Ysera on November 13, 2015, 11:34:43 am
GA1 78
GA2 82
GA3 134/150
Post by: dimitrigots on November 13, 2015, 11:35:42 am
Apparent weightless question made no relation to the point where you have to talk bout that they actually do have weight.
Modulation didn't specify energy transformations, so ill be angry if they take marks off for not stating energy change.
And diagram question in light and matter was pointless, no specifications given.
Post by: odeaa on November 13, 2015, 11:37:07 am
Poor wording of questions as well.Man I'm so salty fuck vcaa
Apparent weightless question made no relation to the point where you have to talk bout that they actually do have weight.
Modulation didn't specify energy transformations, so ill be angry if they take marks off for not stating energy change.
And diagram question in light and matter was pointless, no specifications given.
Post by: Ysera on November 13, 2015, 12:01:28 pm
Man I'm so salty fuck vcaaI interpreted the question wrong, i thought the question said if he is weightless. However i explained it properly and explained the difference between apparent weightlessness and weightlessness, however i wrote No at the start but then i said he did feel weightless.