VCE Physics Question Thread!

[speedy]

Alright, thanks for the help guys.

Another question:
I've seen the formula V₁/V₂ = R₁/R₂ on some notes and stuff but I don't understand how to use it, and when it would be used as opposed to the regular voltage divider formula.

[speedy]

I really don't get this. the question asks to sketch the demodulated signal wave:

This is the answer, the top being the modulated wave... So how come there are "two" signal waves? Would it be wrong to just draw a regular sinusoidal wave?

[PB]

Ok first things first, just do me a favour and completely ignore the answers because I think it is wrong. Either that, or I just don't understand it.
Now, this is an example of amplitude modulation, not frequency modulation, I think we gathered that much.
Secondly, I think the carrier wave is a monoamplitude sinusoidal wave with the same frequency as the mondulated wave.
Thus, the signal wave would have to be the other component of the modulated wave. And the only other wave that can summate with the carrier wave I just described to give you the modulated wave shown would be the positive sin looking graph in the answers (not the negative sin graph).

Why? because only a maximum on the signal wave would boost the positive and negative amplitudes of the carrier wave to give you that first section of that modulated wave.  and only a negative minimum on the signal wave would squeeze the positive and negative amplitudes of the carrier wave to give you that section at 2ms of the modulated wave (that part which looks like a noose had been wrung tightly over the wave)

[PB]

 So how come there are "two" signal waves?

It would be illogical to have the two signal waves looking like what the answer has shown you because they would simply cancel each other out upon wave summation. Thus, the 'modulated wave' and the carrier wave would look exactly the same. Which is why I don't understand what they are trying to say there...

[Yacoubb]

Silly mistakes will be the death of me in this subject. Argh.

Anyone else doing Materials and Structures for their detailed study? It actually looks like a decent detailed study. We then have to do data analysis on materials and structures for this SAC.

Is unit 4 Phys more difficult or easier than U3?

[Rishi97]

Silly mistakes will be the death of me in this subject. Argh.

Anyone else doing Materials and Structures for their detailed study? It actually looks like a decent detailed study. We then have to do data analysis on materials and structures for this SAC.

Is unit 4 Phys more difficult or easier than U3?

We're doing materials and structures for our detailed study as well.. although, I would much prefer to do sound. It 'sounds' more interesting. hehe lol

[Thorium]

We're doing materials and structures for our detailed study as well.. although, I would much prefer to do sound. It 'sounds' more interesting. hehe lol

I love to do materials and structures as it hss to do with my dream job, civil engineering. But in vain, the teacher told i have to do sound coz it is related to the wave model of light.

[speedy]

Ok first things first, just do me a favour and completely ignore the answers because I think it is wrong. Either that, or I just don't understand it.
Now, this is an example of amplitude modulation, not frequency modulation, I think we gathered that much.
Secondly, I think the carrier wave is a monoamplitude sinusoidal wave with the same frequency as the mondulated wave.
Thus, the signal wave would have to be the other component of the modulated wave. And the only other wave that can summate with the carrier wave I just described to give you the modulated wave shown would be the positive sin looking graph in the answers (not the negative sin graph).

Why? because only a maximum on the signal wave would boost the positive and negative amplitudes of the carrier wave to give you that first section of that modulated wave.  and only a negative minimum on the signal wave would squeeze the positive and negative amplitudes of the carrier wave to give you that section at 2ms of the modulated wave (that part which looks like a noose had been wrung tightly over the wave)

Alright thanks heaps. My answer was just the positive sin wave so yeah that's good. However, generally I still don't understand why the modulated wave has both a crest and a trough at the same time.

[PB]

I understand where you are coming from and to be honest, I didn't really understand myself only that it is that way. However, I have never encountered something this in depth with modulation before and it is unlikely that you will get anything like this in the exam or SACs.

[hyunah]

can someone help me with this question 886?
thanks in advance

[Alwin]

can someone help me with this question 886?
thanks in advance

hi   (assuming you are doing sound as your detail study and know standing waves etc)

So the pitch is most important in this question. Now, we know that the pitch is essentially the frequency and that v = λ f

First of all consider the piano:
The piano creates music by the means of a hammer hitting a string, which would create a standing wave along the string of constant λ. Since we know that the speed of sound is greater, this implies that f is also 10% larger. Hence, the piano will sound off-pitch (ie need to be retuned)

Now consider the flute:
The flute creates music by means of a standing wave in the air column, kinda like those questions about standing waves in open pipes. Now, since the pipe has a constant length, this means that λ is also constant for say the fundamental frequency. But since the speed of sound is 10% greater, the flute will also sound too high pitched since the frequency of sound produced is 10% greater.

So, I would choose [A] ...although it has been a while since I touched sound

[hyunah]

yup thanks alwin,

i am also wondering why at short wavelengths the sound is more likely to travel in straight line?

thanks in advance

[lzxnl]

Using VCE terminology:

Smaller wavelengths => smaller wavelength/gap size ratio => less 'diffraction' occurring

Really, a smaller wavelength/gap size ratio just means the wave spreads out less

[Einstein]

for units 1/2 this year, i scored 92% on my radioactivity sac, 100% on Flight  (dual highest) and just recently electricity 98% (highest). Despite this, i have chosen to drop physics, im not enjoying it but i am getting really good marks, if you were in my position what would you do? do you think ive made the right decision to drop out of it for Accounting.

[Thorium]

for units 1/2 this year, i scored 92% on my radioactivity sac, 100% on Flight  (dual highest) and just recently electricity 98% (highest). Despite this, i have chosen to drop physics, im not enjoying it but i am getting really good marks, if you were in my position what would you do? do you think ive made the right decision to drop out of it for Accounting.

If you get similar or better marks in accounting, then go for it