HSC Physics Question Thread

[jamonwindeyer]

i think E = -Gm1m2/r won out i finally got the right answer... mostly because i miss calculated hahaha thankyou guys

Great to hear!!

I very rarely go to mgh though... don't trust its accuracy one bit

I remember I once did a test and found that for altitudes in the hundreds of kilometres, it only makes a difference from the second decimal point or something. Maybe I should do that again

[Caitlyn_]

A 4000kg spaceship is 40.00m long and 8.00m wide when stationary. If the spacecraft now travels at 0.99c in the direction of the length of the craft, calculate, from the frame of reference of an observer on Earth:
a) The spacecraft's length and width at this speed
b) The spacecraft's mass at this speed
c) The time that elapses on the spacecraft if 1 hour passes on earth whilst the craft is travelling at this relativistic speed.

Not sure how to set out and structure this particular question.

[jamonwindeyer]

A 4000kg spaceship is 40.00m long and 8.00m wide when stationary. If the spacecraft now travels at 0.99c in the direction of the length of the craft, calculate, from the frame of reference of an observer on Earth:
a) The spacecraft's length and width at this speed
b) The spacecraft's mass at this speed
c) The time that elapses on the spacecraft if 1 hour passes on earth whilst the craft is travelling at this relativistic speed.

Not sure how to set out and structure this particular question.

Hi Caitlyn! Welcome to the forums! For this question, it will actually be helpful to do a separate calculation of:



It appears in every formula, so we should just do it once to get it done!



So, we can now use this value for other questions. Take your length contraction question for example. We are given the rest length of the spacecraft as 40 metres, that's \(l_0\). We pop that into the formula for length contraction on your reference sheet:



Note that for this question it also wants the width - The width is unaffected! So it is still 8 metres wide; this is because length contraction only occurs in the direction of travel. So it only contracts length-ways.

The other questions are just substitution questions just like above! Take the value we found above, and the value of \(t_0\) or \(m_0\) from the question, then use it to find the relativistic value \(t_v\) or \(m_v\). Does that help?

[Whitey]

A 4000kg spaceship is 40.00m long and 8.00m wide when stationary. If the spacecraft now travels at 0.99c in the direction of the length of the craft, calculate, from the frame of reference of an observer on Earth:
c) The time that elapses on the spacecraft if 1 hour passes on earth whilst the craft is travelling at this relativistic speed.

I tired these myself for practice and I could do a and b without trouble but c gave me some strife.

I originally got but then I realised that time shortens on the really really fast object so I rearranged so I got I'm not sure which is right as I don't think I wholly grasp the concept of time dilation yet. Can someone help please?

[bsdfjnlkasn]

I tired these myself for practice and I could do a and b without trouble but c gave me some strife.

I originally got but then I realised that time shortens on the really really fast object so I rearranged so I got I'm not sure which is right as I don't think I wholly grasp the concept of time dilation yet. Can someone help please?

Hey i'm hoping to help out a bit here - I only recently learnt these formulas but think this would be a good way to apply my knowledge 

So we know that the spacecraft is moving relative to the Earth which means t_o = 1 (as this is the time that has passed on Earth)

Now on to the calculation:



Subbing in known values:



Evaluating:

t_v = 7 hours and 5 minutes

We can also check that our answer is correct as the spacecraft (where v = 0.99c) will experience time dilation. This means our answer needs to be longer than 1 hour. By considering the words which come up in our formulae (contraction and dilation) we can distinguish what the two mean with simple definitions. Contraction means becoming smaller, and dilation means becoming larger.


I hope that this made sense, please excuse my LaTex I have no clue what i'm doing lol

[jamonwindeyer]

Hey i'm hoping to help out a bit here - I only recently learnt these formulas but think this would be a good way to apply my knowledge 

I hope that this made sense, please excuse my LaTex I have no clue what i'm doing lol

Just verifying you got it spot on... Well done!

Rui wrote a cool guide on LaTex, if you are interested. Otherwise I learned from Google if you are keen! Really useful thing to know for Uni

[RuiAce]

Just verifying you got it spot on... Well done!

Rui wrote a cool guide on LaTex, if you are interested. Otherwise I learned from Google if you are keen! Really useful thing to know for Uni

Oh gees. Thanks for reminding me I have to update this

[Whitey]

We can also check that our answer is correct as the spacecraft (where v = 0.99c) will experience time dilation. This means our answer needs to be longer than 1 hour. By considering the words which come up in our formulae (contraction and dilation) we can distinguish what the two mean with simple definitions. Contraction means becoming smaller, and dilation means becoming larger.

Thank you so much!! I get the calculations and where to put tv and to on the formula but my understanding of the concept was not proper, even though we have done it in class.
That paragraph at the end differing between contraction and dilation is pure gold for me! I'm pretty sure that I understand them now!

[Caitlyn_]

Hi Caitlyn! Welcome to the forums! For this question, it will actually be helpful to do a separate calculation of:



It appears in every formula, so we should just do it once to get it done!



So, we can now use this value for other questions. Take your length contraction question for example. We are given the rest length of the spacecraft as 40 metres, that's \(l_0\). We pop that into the formula for length contraction on your reference sheet:



Note that for this question it also wants the width - The width is unaffected! So it is still 8 metres wide; this is because length contraction only occurs in the direction of travel. So it only contracts length-ways.

The other questions are just substitution questions just like above! Take the value we found above, and the value of \(t_0\) or \(m_0\) from the question, then use it to find the relativistic value \(t_v\) or \(m_v\). Does that help?

Thank you so much. I've only just learnt this topic and still wasn't confident on it. So what you have said has helped out a lot!

[jamonwindeyer]

Thank you so much. I've only just learnt this topic and still wasn't confident on it. So what you have said has helped out a lot!

Really glad to hear it! Let us know if you have any further questions

[bsdfjnlkasn]

Thank you so much!! I get the calculations and where to put tv and to on the formula but my understanding of the concept was not proper, even though we have done it in class.
That paragraph at the end differing between contraction and dilation is pure gold for me! I'm pretty sure that I understand them now!

Yay, I'm so glad to have helped!!

[beau77bro]

so my half yearly is coming up and its only focusing on mod 1 and 2, and i have already smashed these out notes wise and everything. im finding i have very limited resources in terms of questions and exam questions. currently im doing surfing just as like a breezy kinda review set of questions, and dot point multiple choice questions because i find multiple choice can be quite tricky and the questions are quite good and also include extension sections that allow me to test extensive knowledge over a give part of the course. but i have no options in terms of actual hsc/exam type long response or harder questions? suggestions??? i can only find a couple of half yearly papers and im not sure that will last very long/ provide a wide enough range of questions to prepare for the exam. suggestions??? honestly links to more half yearly papers would be amazing but i might end up trying some trial papers. but id much rather follow the advice of someone who knows what they are dping hahahahah.

thankyou

[jamonwindeyer]

so my half yearly is coming up and its only focusing on mod 1 and 2, and i have already smashed these out notes wise and everything. im finding i have very limited resources in terms of questions and exam questions. currently im doing surfing just as like a breezy kinda review set of questions, and dot point multiple choice questions because i find multiple choice can be quite tricky and the questions are quite good and also include extension sections that allow me to test extensive knowledge over a give part of the course. but i have no options in terms of actual hsc/exam type long response or harder questions? suggestions??? i can only find a couple of half yearly papers and im not sure that will last very long/ provide a wide enough range of questions to prepare for the exam. suggestions??? honestly links to more half yearly papers would be amazing but i might end up trying some trial papers. but id much rather follow the advice of someone who knows what they are dping hahahahah.

thankyou

Hey! Sounds like you are nice and prepared early on, nice job! As a first option, this site has a collection of Physics papers, including Half Yearly Papers and Trials. Great first stop for practice questions, if you haven't seen it already!

If you are willing to spend a bit of money, you can buy this. It's a set of topic tests for all the core topics in Physics, with detailed solutions to BOSTES style questions handwritten by a Band 6 student. As a disclaimer, that student was me and I wrote the tests, so I'm definitely biased! That said, I do think that it is useful for precisely this purpose

Beyond that, your textbook questions, combined with a bit of extra practice from some combo of those two sources above (and anything else you have access to), should definitely be enough prep for your half yearlies

[beau77bro]

Hey! Sounds like you are nice and prepared early on, nice job! As a first option, this site has a collection of Physics papers, including Half Yearly Papers and Trials. Great first stop for practice questions, if you haven't seen it already!

If you are willing to spend a bit of money, you can buy this. It's a set of topic tests for all the core topics in Physics, with detailed solutions to BOSTES style questions handwritten by a Band 6 student. As a disclaimer, that student was me and I wrote the tests, so I'm definitely biased! That said, I do think that it is useful for precisely this purpose

Beyond that, your textbook questions, combined with a bit of extra practice from some combo of those two sources above (and anything else you have access to), should definitely be enough prep for your half yearlies

OMG WHAT THE TOPIC TESTS ARE READY!!!!!!!?? thats perfect. yassssssss omg thankyou sooo much im buying them now, they are soo good for chem. thankyouuuu, and where are the past papers hahaha sorry?

THANLYOU FOR TELLING ME THIS

how long will it take to deliver?

[jakesilove]

how long will it take to deliver?

Generally, the product will be delivered to you within the week