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March 28, 2024, 07:19:25 pm

Author Topic: HSC Physics Question Thread  (Read 1030374 times)  Share 

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david.wang28

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Re: HSC Physics Question Thread
« Reply #3645 on: February 18, 2019, 10:35:44 pm »
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Hello! Young's experiment was aiming to demonstrate the interference and diffraction of light waves. For that to happen, you need two light 'sources.' That's what the two slits approximate - Two light sources which then interfere with each other to produce the interference patterns Young observed in the experiment! :)
Is it to increase the intensity as well?
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jamonwindeyer

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Re: HSC Physics Question Thread
« Reply #3646 on: February 18, 2019, 10:46:55 pm »
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Is it to increase the intensity as well?

That's not really the reason!! We only get the pattern of maxima/minima when we use two slits. A single slit produces variation in intensity, but it isn't the same thing as the double slit. The double slit is the whole point of making the experiment work :)


david.wang28

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Re: HSC Physics Question Thread
« Reply #3647 on: February 19, 2019, 04:32:32 pm »
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That's not really the reason!! We only get the pattern of maxima/minima when we use two slits. A single slit produces variation in intensity, but it isn't the same thing as the double slit. The double slit is the whole point of making the experiment work :)

(Image removed from quote.)
Thank you! :)
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louisaaa01

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Re: HSC Physics Question Thread
« Reply #3648 on: February 20, 2019, 02:45:40 pm »
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Can someone please help with this question?

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e2503

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Re: HSC Physics Question Thread
« Reply #3649 on: February 20, 2019, 09:11:14 pm »
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Hi :) :)

I`ve been assigned a first hand investigation on kinematics to design an experiment that models the horizontal and vertical components of velocity on the time taken for the flight of a projectile. Whilst i think that the given topic is straight forward, i am unsure about what experiment to conduct that will satisfy the aim.  :'( :'(
If anyone has any suggestions, please send them through :)

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Re: HSC Physics Question Thread
« Reply #3650 on: February 20, 2019, 11:27:39 pm »
+1
Can someone please help with this question?
Thank you.

Hello! This one can basically be broken down as follows:
- Spinning magnet creates changing magnetic flux
- Changing flux results in eddy currents flowing in the disc due to electromagnetic induction
- Lenz's Law says these induced currents will flow to oppose the change that created them. In this context, this means they'll flow to try and attract the magnet back to the same relative position. That won't work, because the magnet is presumably moving in a fixed fashion (assuming the inertia of the magnet is large, basically). So instead, the disc will spin to try and keep up with the magnet!

tl;dr - > Induced eddy currents due to the changing flux cause the disc to spin and 'chase' the magnet to minimise the resultant change in flux ;D

Some reasonably tricky ideas in here, let me know if I can clarify ;D

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Re: HSC Physics Question Thread
« Reply #3651 on: February 20, 2019, 11:34:16 pm »
+1
Hi :) :)
I`ve been assigned a first hand investigation on kinematics to design an experiment that models the horizontal and vertical components of velocity on the time taken for the flight of a projectile. Whilst i think that the given topic is straight forward, i am unsure about what experiment to conduct that will satisfy the aim.  :'( :'(
If anyone has any suggestions, please send them through :)

Hello! For horizontal, you want to launch something horizontally off a raised platform and look at the impact on range. A way to do that is to use a ramp (think hot wheels!) that leads down and launches horizontally off the edge of a table - Changing the height of that ramp above the table will change your horizontal launching velocity :)

Vertical is tougher! Would be keen to hear other people's ideas here? I'd be launching vertically at different velocities and measuring effect on maximum height, but I can't immediately think of a way to predictably vary the vertical velocity? :) I bet there are lots of ideas out there on this!

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Re: HSC Physics Question Thread
« Reply #3652 on: February 21, 2019, 07:30:10 am »
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Hello! For horizontal, you want to launch something horizontally off a raised platform and look at the impact on range. A way to do that is to use a ramp (think hot wheels!) that leads down and launches horizontally off the edge of a table - Changing the height of that ramp above the table will change your horizontal launching velocity :)

Vertical is tougher! Would be keen to hear other people's ideas here? I'd be launching vertically at different velocities and measuring effect on maximum height, but I can't immediately think of a way to predictably vary the vertical velocity? :) I bet there are lots of ideas out there on this!

Thank you so much Jamon :D

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Re: HSC Physics Question Thread
« Reply #3653 on: February 21, 2019, 02:44:54 pm »
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Hello,
I'm stuck with Q 2.2, Q 2.4 and Q 2.5 in the link below. Can anyone please help me with these questions? Thanks ")
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_Himani_

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Re: HSC Physics Question Thread
« Reply #3654 on: February 23, 2019, 05:23:20 pm »
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Hiya,
Can someone please explain why in some cases we write/use the formula to measure electric field strength as E=-delta v/d and others it is simply E=v/d. I understand that delta V is probably the 'more correct' form as it is the change in potential, but I don't understand the negative sign.
Thanks!

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Re: HSC Physics Question Thread
« Reply #3655 on: February 23, 2019, 09:20:18 pm »
+2
Hello,
I'm stuck with Q 2.2, Q 2.4 and Q 2.5 in the link below. Can anyone please help me with these questions? Thanks ")

Hello!

- For 2.2, I can't see the referenced diagram! It is almost certainly just using Speed=Distance/Time? The distance probably comes from multiples of the wavelength and you are given the speed \(v\), so your answer will be something like ?A/v. Maybe?

- For 2.4(b), use \(d\sin{\theta}=m\lambda\), since that is effectively what this situation is. By increasing the frequency, the wavelength is reduced, which means the associated \(\theta\) for minimum disturbance lines is decreased. This is a great simulator for this exact situation ;D

- For 2.4c), places where the wavelets constructively interfere correspond to maxima. Where they destructively interfere corresponds to minima (least disturbance). The diagram will look really similar (identical) to that one I included in an answer a couple of days ago!

Make sure you understand the parallels between 2.4 and the double slit experiment, it's really important to have that conceptualisation set ;D

For 2.5, it's a bit weird to ask for diagrams, I'm guessing they want some similar to that in this video? https://www.youtube.com/watch?v=tlBgvHzppKk
Essentially, Newton thought light was a particle (a corpuscle), and that it reflected by the particle literally bouncing off a surface. Huygen thought it was a wave, reflecting essentially as a consequence of Huygen's Principle (that each point on a wavefront can be thought of as a source of wavelets, and that the leading edge of these wavelets is the actual wavefront). To my interpretation of the syllabus though, that isn't something you need to understand in a whole lot of depth ;D

jamonwindeyer

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Re: HSC Physics Question Thread
« Reply #3656 on: February 23, 2019, 09:44:04 pm »
+2
Hiya,
Can someone please explain why in some cases we write/use the formula to measure electric field strength as E=-delta v/d and others it is simply E=v/d. I understand that delta V is probably the 'more correct' form as it is the change in potential, but I don't understand the negative sign.
Thanks!

Hello! Great question. The \(\frac{-\Delta V}{d}\) form essentially comes from the proper mathematical link between electric field and voltage (meaning it's not something you need to worry about). Essentially, it's because the definition of \(E=\frac{V}{d}\) comes from the work done with a force over a distance, \(W=Fd\). Since \(W=Vq\) and \(F=Eq\):



However, \(W=Fd\) is for work done against a field. In our case, we are considering the work done moving a particle _with_ the field, so we actually use \(W=-Fd\) if we are doing it formally. Carry that through, and that's where the negative comes from.

This is a bit of a bad explanation in itself, but hopefully it gives you some intuition. Don't worry about this in normal working, just trust that it's a consequence of more complicated mathematics and use the formula as you know how to use it ;D

david.wang28

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Re: HSC Physics Question Thread
« Reply #3657 on: February 24, 2019, 10:09:28 pm »
+1
Hello!

- For 2.2, I can't see the referenced diagram! It is almost certainly just using Speed=Distance/Time? The distance probably comes from multiples of the wavelength and you are given the speed \(v\), so your answer will be something like ?A/v. Maybe?

- For 2.4(b), use \(d\sin{\theta}=m\lambda\), since that is effectively what this situation is. By increasing the frequency, the wavelength is reduced, which means the associated \(\theta\) for minimum disturbance lines is decreased. This is a great simulator for this exact situation ;D

- For 2.4c), places where the wavelets constructively interfere correspond to maxima. Where they destructively interfere corresponds to minima (least disturbance). The diagram will look really similar (identical) to that one I included in an answer a couple of days ago!

Make sure you understand the parallels between 2.4 and the double slit experiment, it's really important to have that conceptualisation set ;D

For 2.5, it's a bit weird to ask for diagrams, I'm guessing they want some similar to that in this video? https://www.youtube.com/watch?v=tlBgvHzppKk
Essentially, Newton thought light was a particle (a corpuscle), and that it reflected by the particle literally bouncing off a surface. Huygen thought it was a wave, reflecting essentially as a consequence of Huygen's Principle (that each point on a wavefront can be thought of as a source of wavelets, and that the leading edge of these wavelets is the actual wavefront). To my interpretation of the syllabus though, that isn't something you need to understand in a whole lot of depth ;D
Thank you Jamon! :)
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carlasilvia

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Re: HSC Physics Question Thread
« Reply #3658 on: February 26, 2019, 12:25:25 pm »
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Find the altitude of a satellite in orbit around Earth if its orbital speed is 5.0km/s.

cruzj01

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Re: HSC Physics Question Thread
« Reply #3659 on: February 26, 2019, 01:57:03 pm »
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Okay but this question has me slightly confused,

"Two long, parallel, current-carrying conductors attract each other with a force of F newtons. The current in each, and the distance between them is tripled. Predict the new force between the wires"

heLP