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Author Topic: HSC Physics Question Thread  (Read 1043109 times)  Share 

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jamonwindeyer

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Re: Physics Question Thread
« Reply #2940 on: October 18, 2017, 02:02:11 pm »
+2
Thank you for your reply! So in realistic situations, momentum isn't entirely conserved?

Exactly, I mean it is conserved but it won't appear to be, you'll lose to rotational motion and other stuff ;D

Quote
How would you answer this multiple choice??

The rocket travelling out of earth's atmosphere turns its engines off over a period of 5 seconds, and then immediately ejects the first stage fuel tanks. How does the momentum of the rocket change during this procedure?

a) the momentum of the rocket remains constant

b) the momentum of the rocket remains constant then drops

c) the momentum of the rocket decreases

d) the momentum of the rocket increases and drops

I believe the answer would probably be B - If we ignore friction, the momentum of the rocket is constant while the engines are off. But when it releases the first stage tanks, it has lost mass, so the momentum should drop! :)

austv99

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Re: Physics Question Thread
« Reply #2941 on: October 18, 2017, 02:26:43 pm »
0
Would appreciate help with these questions, thanks.
2002 HSC
23bi
21a
10

owidjaja

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Re: Physics Question Thread
« Reply #2942 on: October 18, 2017, 04:34:39 pm »
0
Hey guys,
So today my teacher was trying to explain gravitational potential energy moving away from Earth and why it reaches zero (or something like that) but I still don't understand it. Can someone please explain it to me?

Thanks :)
2018 HSC: English Advanced | Mathematics | Physics | Modern History | History Extension | Society and Culture | Studies of Religion I

ATAR: 93.60

2019: Aerospace Engineering (Hons)  @ UNSW

KiNSKi01

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Re: Physics Question Thread
« Reply #2943 on: October 18, 2017, 04:44:19 pm »
0
Hey guys,
So today my teacher was trying to explain gravitational potential energy moving away from Earth and why it reaches zero

Thanks :)

Lol another question to add to this. If gravitational field strength follows an inverse square law,how could GPE technically reach zero?
ATAR: 98.20

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'19:
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winstondarmawan

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Re: Physics Question Thread
« Reply #2944 on: October 19, 2017, 01:19:14 pm »
0
Would appreciate help with the following (Q2Q HSC 2009):
https://scontent-syd2-1.xx.fbcdn.net/v/t35.0-12/22664053_1354425641349622_941418257_o.png?oh=e98f61955b94845d8bd99f4edd3b454a&oe=59EA1936
Also, how did Chadwick know that the neutron was neutral simply by LCE and LCM?
TIA.
« Last Edit: October 19, 2017, 02:43:50 pm by winstondarmawan »

fireives1967

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Re: Physics Question Thread
« Reply #2945 on: October 19, 2017, 07:40:49 pm »
0
How would you solve this?

My physics teacher made an excuse to avoid solving it  ;D
Why can't WW3 already happen so we don't have to do the HSCWhy can't WW3 already happen so we don't have to do the HSCWhy can't WW3 already happen so we don't have to do the HSCWhy can't WW3 already happen so we don't have to do the HSCWhy can't WW3 already happen so we don't have to do the HSCWhy can't WW3 already happen so we don't have to do the HSCWhy can't WW3 already happen so we don't have to do the HSCWhy can't WW3 already happen so we don't have to do the HSCWhy can't WW3 already happen so we don't have to do the HSCWhy can't WW3 already happen so we don't have to do the HSC

jamonwindeyer

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Re: Physics Question Thread
« Reply #2946 on: October 19, 2017, 07:48:47 pm »
+3
Would appreciate help with these questions, thanks.
2002 HSC
23bi
21a
10

For 23, End X will be negative. Use the right hand slap rule - With your fingers pointed to the right and your thumb upwards to match the info given, you are slapping into the page. So, positive charges move into the page and negative charges move out of the page - X is negative ;D

For 21, we need acceleration such that the capsule goes from rest to the given speed, \(v\), over the given distance, \(r\). Substitute into the formula from your reference sheet:



For 10, the induced emf will peak when the rate of change of magnetic flux is largest. This happens when the coil is aligned horizontally, parallel to the field. So we need to start at a peak - It must be B or D. We complete one revolution so we should get one induced AC waveform: Answer is B ;D

dannimoussa

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Re: Physics Question Thread
« Reply #2947 on: October 19, 2017, 07:51:38 pm »
+1
How would you solve this?

My physics teacher made an excuse to avoid solving it  ;D

I think I got it but do you answers so I can confirm

jamonwindeyer

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Re: Physics Question Thread
« Reply #2948 on: October 19, 2017, 07:53:34 pm »
+3
Hey guys,
So today my teacher was trying to explain gravitational potential energy moving away from Earth and why it reaches zero (or something like that) but I still don't understand it. Can someone please explain it to me?

Thanks :)

Hey! This guide could be worth a read, but it is basically a matter of convention.

Think of it this way - We know that an object in a gravitational field has GPE. So, the only way to have ZERO GPE, would be to NOT BE in a gravitational field. However, gravitational fields are infinite in size, so you can never actually leave one. So we use a trick - If you go infinitely far away, that will get you out of the field and thus set your GPE to zero.

We want GPE to increase as we move further away from the centre of a field, so that necessitates GPE taking a negative value, so it can increase to zero as defined ;D

Lol another question to add to this. If gravitational field strength follows an inverse square law,how could GPE technically reach zero?

GPE and the force experienced due to a gravitational field (the strength of the field) are two different, but related, quantities. However, neither can actually be zero. Again, it's a mathematical trick to set GPE=0 at an infinite distance (and this would imply \(F_g=0\) as well) - Just something we do ;D

bsdfjnlkasn

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Physics Question Thread
« Reply #2949 on: October 19, 2017, 08:16:41 pm »
+6
How would you solve this?

My physics teacher made an excuse to avoid solving it  ;D

Hey! Hope this is clear :)

« Last Edit: October 19, 2017, 08:30:32 pm by bsdfjnlkasn »

bsdfjnlkasn

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Re: Physics Question Thread
« Reply #2950 on: October 19, 2017, 08:35:36 pm »
+4
Would appreciate help with the following (Q2Q HSC 2009):
https://scontent-syd2-1.xx.fbcdn.net/v/t35.0-12/22664053_1354425641349622_941418257_o.png?oh=e98f61955b94845d8bd99f4edd3b454a&oe=59EA1936
Also, how did Chadwick know that the neutron was neutral simply by LCE and LCM?
TIA.

Hey there!

I'll help with your second question :) Chadwick was able to determine the mass of the neutron to be similar to a proton by using conservation laws. He already knew that it was neutral because the highly penetrating 'radiation' observed by Joliot and Curie remained undeflected in both electric and magnetic fields - this was the property that made them so difficult to be detected in the first place! We don't need to know how the conservation laws were applied but, basically when they were firing the alpha particles at the beryllium, the 'radiation' initially thought to be gamma rays was directed at a sheet of paraffin wax. Because it is proton-rich, when the radiation (neutrons) from the beryllium reached the wax, protons were being ejected. The velocity at which this occurred would have been equal to the incoming velocity (as on such a small scale, the collisions would have been elastic :) ). From there, the mass could be determined (pf=pi=mv) and indeed it confirmed the neutral particle Rutherford proposed when he discovered the nucleus in 1919 :D

If you could please send through a plan of your 6 mark response that would be good because then I can give some more proactive feedback in terms of structure and content (it wouldn't be useful for either of us if I were to straight up give you an answer ;) )
« Last Edit: October 19, 2017, 08:44:12 pm by bsdfjnlkasn »

austv99

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Re: Physics Question Thread
« Reply #2951 on: October 19, 2017, 09:39:10 pm »
0
For 23, End X will be negative. Use the right hand slap rule - With your fingers pointed to the right and your thumb upwards to match the info given, you are slapping into the page. So, positive charges move into the page and negative charges move out of the page - X is negative ;D

For 21, we need acceleration such that the capsule goes from rest to the given speed, \(v\), over the given distance, \(r\). Substitute into the formula from your reference sheet:



For 10, the induced emf will peak when the rate of change of magnetic flux is largest. This happens when the coil is aligned horizontally, parallel to the field. So we need to start at a peak - It must be B or D. We complete one revolution so we should get one induced AC waveform: Answer is B ;D
Im confused about 23. Since positive charges go into the page, isnt Y negative? Since conventional current runs from positive to negative?

jamonwindeyer

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Re: Physics Question Thread
« Reply #2952 on: October 19, 2017, 09:43:01 pm »
+3
Im confused about 23. Since positive charges go into the page, isnt Y negative? Since conventional current runs from positive to negative?

So positive charges are going into the page, towards Y, which would imply that Y is positively charged. So X must be negative. This isn't really a situation to analyse in terms of current, because there isn't a complete path to flow through. Instead, try to think of where the positive charges and negative charges go ;D

winstondarmawan

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Re: Physics Question Thread
« Reply #2953 on: October 19, 2017, 10:31:13 pm »
+3
Hey there!

I'll help with your second question :) Chadwick was able to determine the mass of the neutron to be similar to a proton by using conservation laws. He already knew that it was neutral because the highly penetrating 'radiation' observed by Joliot and Curie remained undeflected in both electric and magnetic fields - this was the property that made them so difficult to be detected in the first place! We don't need to know how the conservation laws were applied but, basically when they were firing the alpha particles at the beryllium, the 'radiation' initially thought to be gamma rays was directed at a sheet of paraffin wax. Because it is proton-rich, when the radiation (neutrons) from the beryllium reached the wax, protons were being ejected. The velocity at which this occurred would have been equal to the incoming velocity (as on such a small scale, the collisions would have been elastic :) ). From there, the mass could be determined (pf=pi=mv) and indeed it confirmed the neutral particle Rutherford proposed when he discovered the nucleus in 1919 :D

If you could please send through a plan of your 6 mark response that would be good because then I can give some more proactive feedback in terms of structure and content (it wouldn't be useful for either of us if I were to straight up give you an answer ;) )

Thank you heaps!
My response would include how the standard model was created in an attempt to explain the nature and composition of matter and it's interaction at it's most fundamental level. This included an explanation of the behaviour of the four fundamental forces which were: x,y,z,w and was explained through the exchange of bosons, a fundamental particle which was postulated to carry force between matter, for example strong nuclear was carried by gluons and gravitational attraction by gravitons. Standard model also deconstructed electrons, protons and neutrons into even smaller fundamental particles that were quarks and leptons. There were 6 types of each (list types) and protons comprised of up,up,down quarks and neutrons consisted of down,down,up quarks which explained their elementary charge. (Here, would also talk about the +2/3 and -1/3 charge of up/down quarks). Electrons were a special case of leptons, particles with negligible rest mass that interacted through weak nuclear and EM attraction.
I'd make a judgement about the impact of this on understanding, then say 'despite this there are flaws and questions that arise':
* Could not explain why there were 6 types of quarks and leptons, as well as their charge.
* Gravitons were only predicted, and not yet discovered. This was similar case with the Higgs Boson, which was only predicted by the standard model and found using extensive research and experimentation.
Please tell me what I am missing and how to improve this response. :)
Also, I would appreciate a rundown on all the scientists which contributed to the Manhattan Project and their explicit contributions.
Thanks again!

bsdfjnlkasn

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Re: Physics Question Thread
« Reply #2954 on: October 19, 2017, 11:16:28 pm »
+3
Thank you heaps!
My response would include how the standard model was created in an attempt to explain the nature and composition of matter and it's interaction at it's most fundamental level. This included an explanation of the behaviour of the four fundamental forces which were: x,y,z,w and was explained through the exchange of bosons, a fundamental particle which was postulated to carry force between matter, for example strong nuclear was carried by gluons and gravitational attraction by gravitons. Standard model also deconstructed electrons, protons and neutrons into even smaller fundamental particles that were quarks and leptons. There were 6 types of each (list types) and protons comprised of up,up,down quarks and neutrons consisted of down,down,up quarks which explained their elementary charge. (Here, would also talk about the +2/3 and -1/3 charge of up/down quarks). Electrons were a special case of leptons, particles with negligible rest mass that interacted through weak nuclear and EM attraction.
I'd make a judgement about the impact of this on understanding, then say 'despite this there are flaws and questions that arise':
* Could not explain why there were 6 types of quarks and leptons, as well as their charge.
* Gravitons were only predicted, and not yet discovered. This was similar case with the Higgs Boson, which was only predicted by the standard model and found using extensive research and experimentation.
Please tell me what I am missing and how to improve this response. :)
Also, I would appreciate a rundown on all the scientists which contributed to the Manhattan Project and their explicit contributions.
Thanks again!


Hey there!

Awesome stuff :D There are just a few extra things that I would like to mention, hopefully they make sense!

First things first, we need to figure out what the question's asking: it's asking us to link theories (i.e. predictions) with experiments (i.e. results from particle accelerators) as they relate to the SM of M.

So you're right by starting with a definition of the standard model and you have all the right stuff for it:
a) Explained the composition of matter on a fundamental level
b) Accounted for the interactions between particles

Then I'd go into how it organised matter into (would help cut your response down a bit. After you quickly run past the structure of the SM of M, then we go into the next part of the question which wants us to talk about experiments)

1. Fermions
- Leptons: Don't experience strong nuclear force
(can list if you want: electron, muon, tau and their neutrino pair)
- Quarks: Experience all four fundamental forces (i.e. strong/weak nuclear force, electromagnetic and gravity)
(Hadrons --> Baryons and Mesons)

2. 'Force Carrier' Bosons (particles through which forces are mediated)
- Zo, X+, X- (I personally haven't come across W or Y.. what are they? :) )

3. And all their anti-particles

Some annotations on your response:
This included an explanation of the behaviour of the four fundamental forces which were: x,y,z,w and was explained through the exchange of bosons, a fundamental particle which was postulated to carry force between matter, for example strong nuclear was carried by gluons and gravitational attraction by gravitons. Standard model also deconstructed electrons, protons and neutrons into even smaller fundamental particles that were quarks and leptons Be careful here. Standard model didn't 'deconstruct' electrons, they're a fundamental particle. What the model did do, was classify the electron as leptons. Also, I would rephrase and say "nucleons were also predicted to be comprised of smaller fundamental particles called quarks". There were 6 types of each (list types) and protons comprised of up,up,down quarks and neutrons consisted of down,down,up quarks which explained their elementary charge. (Here, would also talk about the +2/3 and -1/3 charge of up/down quarks) Although this detail really shows you know your stuff, you need to be including more of the experimental aspect of the question to really be addressing it. So we could do a bit more in terms of ensuring that all the info is relevant. Electrons were a special case of leptons, particles with negligible rest mass that interacted through weak nuclear and EM attraction Good, but unfortunately irrelevant.

Here we need to mention the use of particle accelerators :)

The standard model is the product of predictions and experimental results (i.e. research). Linear accelerators and cyclotrons were initially used to 'probe' the structure of matter as new particles were created from these high speed collisions. These technologies were very effective, but now we have even better synchrotrons and particle accelerators (LHC) which are used more widely.

I'd make a judgement about the impact of this on understanding, then say 'despite this there are flaws and questions that arise': This is perfect! Super important to mention
* Could not explain why there were 6 types of quarks and leptons, as well as their charge.
* Gravitons were only predicted, and not yet discovered. This was similar case with the Higgs Boson, which was only predicted by the standard model and found using extensive research and experimentation.
Important to also note that the SM of M is a quantum-mechanical model which makes it incompatible with Einstein's general theory relativity. This prevents gravity from unifying the forces
« Last Edit: October 19, 2017, 11:40:10 pm by bsdfjnlkasn »