February 25, 2020, 04:25:14 pm

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#### Coolmate

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##### Re: HSC Physics Question Thread
« Reply #3885 on: February 09, 2020, 12:30:32 pm »
0
Hey! Sorry that this answer is a little late, but the inner Van Allen belt appears to be at a 1000km altitude or above in most areas, which would traditionally be considered higher than a LEO. Wikipedia (lol) tells me that some places it can have concentrations at lower altitudes though so in some places maybe? This is outside syllabus scope though

Also, I was just wondering if someone could please help me on how I should structure a response, in a Physics way, that asks me to "Discuss two things".

Thanks again!
Coolmate
« Last Edit: February 09, 2020, 01:26:57 pm by Coolmate »
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#### milie10

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##### Re: HSC Physics Question Thread
« Reply #3886 on: February 10, 2020, 12:07:14 am »
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Your working is on the right track! We get the EMF by relating it to the change in flux, which you have spotted. Note the initial flux is zero (no magnetic field). So the change in flux is basically just whatever flux is from the current, divided by the time taken to switch that on (0.1s). The one missing piece for you I think is the formula which gives you a magnetic flux produced by a current in a solenoid. First, remember the difference between flux and flux density, $\phi=BA$. That in mind, the formula you need is a Prelim formula:

$B=\frac{\mu_0 NI}{L}$

So in summary the steps are:

- Figure out the strength of the magnetic field produced by the larger solenoid using the formula above (reference your Prelim notes!)
- Figure out how much flux this introduces in the smaller solenoid using $\phi=BA$. Remember the $A$ should be the area for the smaller solenoid because that is where the current is induced!
- Use this flux (also the change in flux, remember the initial flux is zero!) in $\epsilon=\frac{\Delta \phi}{\Delta t}$ to determine the resultant induced emf.

Hopefully this is enough to let you have a go - It's a tough question (B6 level) so awesome job for wanting to explore it and understand it properly

thanks so much!! this helped a lot

#### mani.s_

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##### Re: HSC Physics Question Thread
« Reply #3887 on: February 14, 2020, 08:00:39 pm »
0
Hi, could someone confirm my answer and working out for this question? Thanks

$\Delta E=W\\ \Delta E=-\frac{GMm}{2}(\frac{1}{r_f}-\frac{1}{r_i})\\ 1000000=-\frac{GMm}{2}(\frac{1}{2\times 10^7}-\frac{1}{1\times 10^7})\\ 1000000=\frac{GMm}{4\times 10^7}\\ 4\times 10^{13}=GMm\\ \Delta E=-\frac{GMm}{2}(\frac{1}{r_f}-\frac{1}{r_i})\\ \Delta E=-\frac{4\times 10^{13}}{2}(\frac{1}{8\times 10^7}-\frac{1}{1\times 10^7})\\ \Delta E=1750000 J=1.75 MJ\\ W=1.75 MJ$

#### fun_jirachi

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##### Re: HSC Physics Question Thread
« Reply #3888 on: February 14, 2020, 11:34:37 pm »
+3
Hi, could someone confirm my answer and working out for this question? Thanks

$\Delta E=W\\ \Delta E=-\frac{GMm}{2}(\frac{1}{r_f}-\frac{1}{r_i})\\ 1000000=-\frac{GMm}{2}(\frac{1}{2\times 10^7}-\frac{1}{1\times 10^7})\\ 1000000=\frac{GMm}{4\times 10^7}\\ 4\times 10^{13}=GMm\\ \Delta E=-\frac{GMm}{2}(\frac{1}{r_f}-\frac{1}{r_i})\\ \Delta E=-\frac{4\times 10^{13}}{2}(\frac{1}{8\times 10^7}-\frac{1}{1\times 10^7})\\ \Delta E=1750000 J=1.75 MJ\\ W=1.75 MJ$

You're very very close!
It's just a trick in the wording - it asks how much more work is required to move the object (note that 'more work' is very important!). This just means you've got to subtract 1MJ from 1.75MJ as calculated.

Hope this helps
Failing everything, but I'm still Flareon up.

HSC 2018: Modern History [88] | 2U Maths [98]
HSC 2019: Physics [92] | Chemistry [93] | English Advanced [87] | Maths Extension 1 [98] | Maths Extension 2 [97]
ATAR: 99.05

UCAT: 3310 - Verbal Reasoning [740] | Decision Making [890] | Quantitative Reasoning [880] | Abstract Reasoning [800]

#### mani.s_

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##### Re: HSC Physics Question Thread
« Reply #3889 on: February 15, 2020, 12:14:14 am »
0
Ahhh, thank you so much!!!!

#### mani.s_

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##### Re: HSC Physics Question Thread
« Reply #3890 on: February 17, 2020, 04:31:10 pm »
0
Hi, I was wondering if I needed to know the slingshot effect for the HSC??? Would I be able to use to explain stuff for long responses?

Thanks

#### Coolmate

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##### Re: HSC Physics Question Thread
« Reply #3891 on: February 17, 2020, 08:36:59 pm »
0
Hi Everyone,

Could someone please help me break down this part of my marking criteria for my depth study and what it means:

Questioning and predicting
--> Identifying scientific inaccuracies

Identifies and proposes valid scientific mistakes and develops appropriate improvements, (asks questions and makes evidence based predictions) (5 MARKS)

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#### jamonwindeyer

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##### Re: HSC Physics Question Thread
« Reply #3892 on: February 17, 2020, 09:11:16 pm »
+4
Hi, I was wondering if I needed to know the slingshot effect for the HSC??? Would I be able to use to explain stuff for long responses?

Thanks

Hey! Nah, the slingshot effect isn't necessary knowledge for the new syllabus (you could use it as an example of a collision for Year 11 momentum stuff, but you won't be assessed on that in Year 12)

#### jamonwindeyer

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##### Re: HSC Physics Question Thread
« Reply #3893 on: February 17, 2020, 09:13:03 pm »
+4
Hi Everyone,

Could someone please help me break down this part of my marking criteria for my depth study and what it means:

Questioning and predicting
--> Identifying scientific inaccuracies

Identifies and proposes valid scientific mistakes and develops appropriate improvements, (asks questions and makes evidence based predictions) (5 MARKS)

This wants you to be critical! What is missing from experiments you are referencing? What errors were made, if any? How could this error have been caught? Basically, for every 'key experiment/finding' you talk about, or key source you reference, don't just take it at face value. Consider it critically and decide whether anything is 'wrong.' If it is, that's okay, but make it a discussion point!

#### Coolmate

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##### Re: HSC Physics Question Thread
« Reply #3894 on: February 17, 2020, 09:59:15 pm »
0
This wants you to be critical! What is missing from experiments you are referencing? What errors were made, if any? How could this error have been caught? Basically, for every 'key experiment/finding' you talk about, or key source you reference, don't just take it at face value. Consider it critically and decide whether anything is 'wrong.' If it is, that's okay, but make it a discussion point!

Hey Jamon!

Thankyou so much for the clarification!

Also, when it says "Makes evidence based predictions", I am analysing a movie so does this mean I should research and provide evidence to support my answer?

Thanks again,
Coolmate
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#### mani.s_

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##### Re: HSC Physics Question Thread
« Reply #3895 on: February 17, 2020, 10:43:12 pm »
+1
Hey! Nah, the slingshot effect isn't necessary knowledge for the new syllabus (you could use it as an example of a collision for Year 11 momentum stuff, but you won't be assessed on that in Year 12)
thank you so much Jamon, you the man!!!
« Last Edit: February 18, 2020, 11:05:14 pm by mani.s_ »

#### jamonwindeyer

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##### Re: HSC Physics Question Thread
« Reply #3896 on: February 18, 2020, 07:44:07 pm »
+3
Hey Jamon!

Thankyou so much for the clarification!

Also, when it says "Makes evidence based predictions", I am analysing a movie so does this mean I should research and provide evidence to support my answer?

Thanks again,
Coolmate

Correct! "This isn't right, because Reputable Source X tells us that..." or "This is a flawed viewpoint, because Law of Physics that makes it flawed. Or something like that you need the BECAUSE in there, the justification, based on evidence

#### Coolmate

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##### Re: HSC Physics Question Thread
« Reply #3897 on: February 19, 2020, 05:21:49 pm »
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Correct! "This isn't right, because Reputable Source X tells us that..." or "This is a flawed viewpoint, because Law of Physics that makes it flawed. Or something like that you need the BECAUSE in there, the justification, based on evidence

Thanks Jamon! This makes a lot more sense now
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#### Coolmate

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##### Re: HSC Physics Question Thread
« Reply #3898 on: February 24, 2020, 08:47:32 pm »
0
Hi Everyone,

Just a quick question, I was just wondering if anyone knew of any High Earth Orbiting satellite examples

Thanks
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#### milie10

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##### Re: HSC Physics Question Thread
« Reply #3899 on: February 24, 2020, 10:58:53 pm »
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Hi Everyone,

Just a quick question, I was just wondering if anyone knew of any High Earth Orbiting satellite examples

Thanks

Hi Coolmate!!
Geostationary (equatorial) satellites or Geosynchronous satellites (not equatorial, but have the same period and altitude as a geostationary satellite) are the general names of high earth orbiting satellites. Characteristics include:

• Altitude of 36000km
• Orbital period of 24 hours/day
• Used for communication

I'm not sure if you wanted specific real life examples of these satellites- maybe someone else can pop in for that! However, I believe these low and high earth satellites only need to be related to their properties (altitude, orbital period and orbital plane) and uses based on the syllabus.

Hope that helps!