Post by: Kiro Kompiro on August 10, 2011, 11:26:02 pm
My school says we have to study Einstein's Relativity and the Synchrotron as the 3 and 4 detailed studies next year.
Looking at past exam reports, Einsteins Relativity has the least number of students answering questions correctly. Materials is the most popular with highest number of students answering correctly.
Also whats the point of studying the synchrotron when I heard they were closing it down.
I want to opt out of relativity, and study materials. Looks too hard. And Sound instead of synchrotron. Not sure if I can though.
What do people think
Post by: Lasercookie on August 10, 2011, 11:38:51 pm
It is the greatest topic covered in the entire course, you will be sorry that you didn't learn it.
It is not too hard. The relativity exam questions prior to this year were pretty damn easy (I got close to 100% on them most of the time). Admittedly I did struggle on relativity in the midyear, but that was due to my very very poor time management during the exam (left it for the last ten minutes like I did on trial exams - big mistake, should have done it first up) .
Post by: Lasercookie on August 11, 2011, 12:27:42 am
First, your teacher is obviously a great physics teacher if he is willing to teach Special Relativity. He's been able to look beyond the statistics, not be a sheep and teach you the better content. If you enjoy the kind of stuff in structures and materials, there's enough of that kind of stuff in motion.
SR is some fairly big ideas to grasp, but quite quickly you will 'click' and it'll all appear intuitive to you. You have probably heard of the concept of 'scientific beauty' before, it's kind of an odd idea until you really see it and understand it. When I 'clicked' and really got my head around it I finally understood what 'scientific beauty' is. Special relativity just makes so much sense, and the way it has been set out is brilliant. Contrary to what you may know of Einstein's work, e=mc^2 wasn't the part that I found most brilliant.
Answering questions is not difficult at all, to answer an SR question you just need to remember the 4 or 5 basic principles and with a lot of the exam questions you could eliminate 2 or 3 of the options pretty much immediately. The mathematics involved is ridiculously simple.
You really will gain a better appreciation/understanding for the work of Newton, Maxwell, Einstein/physics in general. The SR detailed study is pure awesome.
About the synchroton detailed study, we're studying sound so I can't really say much about it. But just because the Australian Synchrotron may close doesn't mean that all particle accelerators are going to close. If your teacher is one of those few teachers that is willing to teach Relativity, I would trust his opinion and just go with it.
Finally, from what I gathered, the only reason you want to switch out of Relativity is because the statistics have told you that more people do it and therefore more score better (in S&M). I've already outlined why relativity isn't as hard as you think (it is just VCE physics after all). If the only thing you want is an easy score, opt out of physics completely.Don't bother with it. There's better stuff you could be doing with your time. Physics can be quite excruciatingly painful if you don't enjoy it. I'm sorry if that seems harsh, but I find it hard to understand how someone could even consider the notion of rejecting the opportunity to learn about one of the greatest physics discoveries yet.
Maybe it's because you're not aware of some of the implications of special relativity. Watch this: http://www.youtube.com/watch?v=A0jiY-CZ6YA. If that does not spark your curiosity, I don't believe anything in the physics course will.
I think I'm done now.
edit: fixed up my annoying spelling mistakes
Post by: Shark 774 on August 11, 2011, 10:23:45 am
I'm in year 11.
My school says we have to study Einstein's Relativity and the Synchrotron as the 3 and 4 detailed studies next year.
Looking at past exam reports, Einsteins Relativity has the least number of students answering questions correctly. Materials is the most popular with highest number of students answering correctly.
Also whats the point of studying the synchrotron when I heard they were closing it down.
I want to opt out of relativity, and study materials. Looks too hard. And Sound instead of synchrotron. Not sure if I can though.
What do people think
My class did structures & materials in unit 3 and are doing sound in unit 4. I chose to do relativity and LOVED it in Unit 3, and am going to do the synchrotron this semester. I would only recommend relativity if you are a keen physics student, if not then I have heard the further electronics is very helpful because it is relevant to parts of both unit 3 and 4. And as for the synchroton, it is much much more relevant to any of unit 4 than sound or photonics.
Post by: Lasercookie on August 11, 2011, 03:48:04 pm
... I would only recommend relativity if you are a keen physics student ...I disagree, most of my class are not what you would call 'keen' physics students yet they grasped relativity quite well.
It might have been more difficult for you, since you did it by yourself, but doing it with the rest of the class and the teacher
explaining makes relativity a breeze. Self-studying any physics (or any science or maths for that matter) would require a keen
student.
Post by: b^3 on August 11, 2011, 04:38:21 pm
At my school for physics, self studying isn't optional if you want to pass.... I would only recommend relativity if you are a keen physics student ...Self-studying any physics (or any science or maths for that matter) would require a keen
student.
Post by: tony3272 on August 11, 2011, 04:49:24 pm
Haha that's exactly the same for my school.At my school for physics, self studying isn't optional if you want to pass.... I would only recommend relativity if you are a keen physics student ...Self-studying any physics (or any science or maths for that matter) would require a keen
student.
Our class is simply us watching a powerpoint of the Jacaranda textbook copy and pasted, cutting out heaps of stuff :-\
Post by: b^3 on August 11, 2011, 04:52:14 pm
The Jacaranda book is complete rubbish. Does your teacher also confuse you and tell you the wrong things like ours does?Haha that's exactly the same for my school.At my school for physics, self studying isn't optional if you want to pass.... I would only recommend relativity if you are a keen physics student ...Self-studying any physics (or any science or maths for that matter) would require a keen
student.
Our class is simply us watching a powerpoint of the Jacaranda textbook copy and pasted, cutting out heaps of stuff :-\
Post by: Lasercookie on August 11, 2011, 04:53:30 pm
At my school for physics, self studying isn't optional if you want to pass.Haha, that a reflection of the fact that your teacher isn't too great though?
Still I strongly believe that the OP should stick with the relativity detailed study.
In the case that his teacher isn't actually that great, the teacher wouldn't be that much better off teaching S&M over relativity.
The students wouldn't be that much better off - they'd still have to do a large amount of self-studying either way with a bad teacher.
However, if the OP's teacher is a good teacher, then he's found himself in the lucky situation of having a good physics teacher that has made the choice to teach the best content in the course.
Post by: b^3 on August 11, 2011, 04:59:50 pm
There is hardly any good physics teachers out there because well, lets be honest, if you are good at physics you don't go into teaching (or rarely anyway). Then there is those unique brillant sparks of human beings who can open up the world of thought for us.At my school for physics, self studying isn't optional if you want to pass.However, if the OP's teacher is a good teacher, then he's found himself in the lucky situation of having a good physics teacher that has made the choice to teach the best content in the course.
Sorry for going off topic a bit.
I didn't do relativity but I would like to have done it. I'd say try relativity out and (since you are yr 11), if you struggle you can always change to another one before your class even gets up to the point of starting one.
Post by: Kiro Kompiro on August 11, 2011, 05:36:51 pm
i have read a bit on relativity and I know its one of the most important discoveries in science.
And I do enjoy physics, although I've only studied motion and some electricity, mainly circuits.
My concern with relativity is that I learn by "seeing" what is going in my mind. I've read some notes on the net and I find it difficult to visualize different frames moving with respect to each other, and calculating the times and distances. It doesn't deal with everyday experience.
Looking at the examiners reports also concerned me: of all the optional study units, this topic gets the least number of students getting the right answer. Some questions are answered correctly by only 15% of the students. Hardly ANY question is answered correctly by 75% of the students.
I want to learn but I don't want to lose marks just by choosing a more difficult option.
I don't even know if its possible to choose another option anyway at my school.
Post by: Lasercookie on August 11, 2011, 06:00:29 pm
I'm going to again state that I found VCAA 2009 to be ridiculously easy and VCAA 2010 was not that challenging either (but not as easy as 2009). The majority of trial exams did not having challenging relativity questions (except for a select few). If you're after a good score, you'd be doing a lot of study anyway - I don't believe you will be compromised by taking relativity.
The only thing you can really do now is talk to your teacher. Most teachers would not be willing to let you study something different (as that would mean you would have to sit a different SAC etc.) and could put your marks in jeopardy since you would be self-studying.
I can't really say much for your personal learning methods, but I reckon having your teacher explain things would be better than trying to learn by reading. Have a talk to your teacher and see what their opinion is. You obviously know my opinion by now.
Post by: b^3 on August 11, 2011, 09:28:00 pm
The only thing you can really do now is talk to your teacher. Most teachers would not be willing to let you study something different (as that would mean you would have to sit a different SAC etc.) and could put your marks in jeopardy since you would be self-studying.I was under the impression that even if you did a different topic, you still have to do the sac on the topic the class did. That is how it was for further last year. Or maybe it's just my school.
Post by: Lasercookie on August 11, 2011, 09:48:07 pm
Shark would be the one to talk to about that - I'm pretty sure he got to do a different SAC to the rest of the class.The only thing you can really do now is talk to your teacher. Most teachers would not be willing to let you study something different (as that would mean you would have to sit a different SAC etc.) and could put your marks in jeopardy since you would be self-studying.I was under the impression that even if you did a different topic, you still have to do the sac on the topic the class did. That is how it was for further last year. Or maybe it's just my school.
It would vary from teacher-to-teacher though.
Post by: Egregious Customer on August 11, 2011, 11:37:21 pm
About the synchrotron, it was introduced as a promotional topic because the technology is quite new and also Victoria's pride. Sadly, not many teachers fully understand the technology to be able to deliver the content adequately. When the topic was first introduced, experts in the field had to run a couple of forums/seminars/workshops to educate physics teachers across the state about the synchrotron.
I'm actually confident that there are more teachers out there who are more comfortable with special relativity than synchrotron. However, special relativity is a very difficult subject to teach, and the teachers usually have to weigh it up against the class and see whether it is wise to teach it. There is no point teaching a more interesting topic when most of the class aren't going to understand it.
Having said all that, special relativity and synchrotron are probably the better topics out of the bunch, and probably the easiest as well once you understand it. With special relativity, you just need to know how to apply a few simple formulas, and similarly with synchrotron. This is because the topics are conceptually difficult, so it would be cruel and unfair for them to throw you too many surprises. On the other hand, the other topics can still be tricky even if you understand the content.
Post by: Kiro Kompiro on August 12, 2011, 09:40:11 pm
Post by: Lasercookie on August 12, 2011, 10:15:04 pm
I looked at the twin paradox video. Conceptually i get stuck on this point: If the rocket moves at a velocity of say 0.8c as seen from the twin on earth, then the twin on Earth sees the time on the rocket go slower. BUT from the frame of reference of the rocket, the earth is moving away at 0.8c. Why doesn't the twin in the rocket see the time on earth run slower?That's time dilation.
If I remember correctly, the twin on the rocket does see time on the Earth run slower.
I just watched through the video then and I don't believe it suggested anything of the kind?
It did mention that you could say that the Earth is moving away as seen by the twin in the rocket and then went on to say that only the rocket physically experienced acceleration. It would just appear to the twin on the rocket that Earth is moving at 0.8c (and therefore sees time running slower). So if you calculated this, the paradox is that who would actually end up being the older twin.
The paradox is resolved because the twin in the rocket would have to decelerate/accelerate non-uniformly to turn around (therefore no longer being an inertial reference frame) and not adhering to special relatvity. Non-inertial frames are covered by general relativity I believe.
This is a good resource for SR that I used extensively.
http://www.phys.unsw.edu.au/einsteinlight/
Specifically about time dilation (and the twin paradox) there is:
http://www.phys.unsw.edu.au/einsteinlight/jw/module4_twin_paradox.htm
Post by: Kiro Kompiro on August 13, 2011, 11:15:09 am
So what if the rocket goes on a one-way trip at 0.8c to a base located 4 light years away. He flies past the base without slowing.
As measured on earth, can we simply use velocity=distance/time to calculate at the instant the rocket flies past the base? ie On Earth do 4c/0.8c=5 years elapse until the rocket ship gets to the base?.
How many years will a clock on the rocket read at as the rocket flies past the base? Is it =5*sqr(1-0.8c^2/c^2)=5*0.67=3 years?
Post by: pi on August 13, 2011, 11:17:38 am
Post by: Lasercookie on August 13, 2011, 11:33:18 am
you can use v=x/t, x=vt, t=x/v for when you're trying to solve for proper velocity, time, displacement etc.
This is where it gets a bit confusing, trying to figure out which frames are proper or not.
So if you're taking Earth to be the proper reference frame, then yes 4c/0.8c = 5 years.
What happens next depends on who is observing.
A clock on the rocket - observed by the person inside the rocket - will not observe the effects of relativity. To him/her, time will flow as normal. This is stated in one of the postulates (first one I think) - "The laws of physics are the same in any inertial frame, regardless of position or velocity".
However, if the person on the Earth (outside the reference frame) was to look at the clock on the rocket - they will observe the effects of relativity.
(I just like to write everything out to get my head around the problem)
So
So
I haven't done any relativity problems since the exam and I've already started to get a bit rusty on my SR knowledge :(. I may have made some errors somewhere, but I'm pretty sure what I've said is correct.
Post by: Kiro Kompiro on August 13, 2011, 12:38:52 pm
Before I start, I have to say good work - it looks like you've been able to get your head around relativity pretty well.
you can use v=x/t, x=vt, t=x/v for when you're trying to solve for proper velocity, time, displacement etc.
This is where it gets a bit confusing, trying to figure out which frames are proper or not.
Yes this where I think I lose my train of thought. Is there a simplified definition (or method to follow to work out ) of proper time and proper length
So if you're taking Earth to be the proper reference frame, then yes 4c/0.8c = 5 years.
What happens next depends on who is observing.
A clock on the rocket - observed by the person inside the rocket - will not observe the effects of relativity. To him/her, time will flow as normal. This is stated in one of the postulates (first one I think) - "The laws of physics are the same in any inertial frame, regardless of position or velocity".
So- according to the person in the rocket- looking at the clock in the rocket, the trip takes 5 years as well?
However, if the person on the Earth (outside the reference frame) was to look at the clock on the rocket - they will observe the effects of relativity.
(I just like to write everything out to get my head around the problem)
So(can't be bothered typing up the calculations - but you ended up getting 0.67?) -
sorry my bad gamma should have been 1.67 instead of 0.67
Also have to point you shouldn't ever use rounded off answers mid-answer. Only round off/apply sig figs for the final answer.
So
So this is the time that elapses on clock on the rocket as seen by someone on earth looking into the rocket?
Post by: Lasercookie on August 13, 2011, 01:51:21 pm
Yes this where I think I lose my train of thought. Is there a simplified definition (or method to follow to work out ) of proper time and proper lengthThis is really a skill you'll pick up by practicing questions. Sometimes questions will explicitly state the proper reference frame, sometimes it'll be implied. It's really tricky at first - as it depends on the wording of the question.
"So what if the rocket goes on a one-way trip at 0.8c to a base located 4 light years away. He flies past the base without slowing."
I took 4 light years to be the proper length. It would have said something about the length being contracted or something if they meant relativistic length.
If you then derived the proper time using the point of view of Earth (using t=x/v), that means that 5 years is the proper time.
You could have taken it from the point of view of the rocket though. So he's travelling a distance of 4 ly at 0.8c
To find out the dilated time that
blah blah blah and you get the same answer.
If you knew the dilated time, you could figure out t_0 that way etc.
Have a go at the relativity section of VCAA 2009.
http://www.vcaa.vic.edu.au/vcaa/vce/studies/physics/pastexams/2009/2009physics1-w.pdf
You can definitely do Q1-Q6. Skip Q7 and Q8 (they are about energy-mass equivalence, you might know Q8 though),
Q9 and Q10 are about time dilation/length contraction again, Q11 - maybe (it's about work/masses again) and then Q12 and 13 definitely.
So basically every question except for Q7, Q8, Q11 I reckon you would be able to do. Most of them involve differentiating between proper and relativistic values as well. Hopefully that will give you a better idea. There's no tricky questions there though.
http://www.tsfx.com.au/vic/vcedgeonline/trialexampapers/index.htm
If you want another simple relativity section (slightly trickier worded questions from memory), I'm pretty sure you should be pretty good with TSFX 2010. Again skip the simultaneity, mass-equivalence, kinetic energy questions (unless you've learnt about them already). TSFX exams are available freely on their website, you have to register for free though (bugmenot.com should have some working usernames/passwords if you can't be bothered registering).
http://engageeducation.org.au/practice-exams/physics/74-unit-3-physics-practice-exam
The engage education one also had some pretty easy questions (the last couple were about masses/kinetic energy though). That one is also free off their site - don't need to register.
I had these simple rules on my cheatsheet:
So- according to the person in the rocket- looking at the clock in the rocket, the trip takes 5 years as well?Yep, people travelling at relativistic speeds will observe everything in their reference frame to be behaving normally.
So this is the time that elapses on clock on the rocket as seen by someone on earth looking into the rocket?Yes, they see the rocket moving slower.
Post by: Kiro Kompiro on August 13, 2011, 03:06:50 pm
Post by: Lasercookie on August 13, 2011, 03:27:38 pm
You are a legend laser! Many thanks!Thanks :)
So I hope you've decided to stick with relativity and synchrotron. If you can learn all that by yourself, you should be perfectly fine understanding relativity when the teacher explains it.
Post by: Shark 774 on August 13, 2011, 11:16:47 pm
... I would only recommend relativity if you are a keen physics student ...I disagree, most of my class are not what you would call 'keen' physics students yet they grasped relativity quite well.
It might have been more difficult for you, since you did it by yourself, but doing it with the rest of the class and the teacher
explaining makes relativity a breeze. Self-studying any physics (or any science or maths for that matter) would require a keen
student.
Ah ok fair point. I just got the impression, from some kids I spoke to who had to do it, that they found it very strange and weren't keen physics students, hence couldn't be bothered to put in the extra effort required to fully understand it and just learned how to apply the formulas, thus making it very dull and easy to get tricked on.