Physics Predictions/Thoughts (7 Viewers)

[barnyard]

This also isn't the first time they've worded questions poorly.

If you took their word literally, you would've put R, which would've been given 0/3 marks.'

this is such a shit example, they obviously meant inverse function, they have never asked about just an inverse in general bc everything has an inverse relation. also, if you just put R ofc ur gonna get 0 or 1, you need to explain it.
whereas for the cylinder physics question it's actually unclear what they want bc they havent asked questions like that before. the cylinder q is bad bc it wasnt previously tested in a way where everyone knows how to answer it even if they word it wrong.

 

[Trial&Error]

Do we need to know every detail on how nuclear fusion/fission reactors work? Pleaseeee say no.

 

[C2H6O]

Do we need to know every detail on how nuclear fusion/fission reactors work? Pleaseeee say no.

im pretty sure fusion reactions are only a theoretical thing rn
fission reactors would be good cause you can confuse the roles of the parts, but i found this video quite helpful:

not 100% relevant but the visualisation is useful
skip to 0:58, and everything up to 8:50 is useful, after that you can probably stop watching cause he starts talking about chernobyl but stay if you want to see the reactor working

 

[BionicMango]

this is such a shit example, they obviously meant inverse function, they have never asked about just an inverse in general bc everything has an inverse relation. also, if you just put R ofc ur gonna get 0 or 1, you need to explain it.
whereas for the cylinder physics question it's actually unclear what they want bc they havent asked questions like that before. the cylinder q is bad bc it wasnt previously tested in a way where everyone knows how to answer it even if they word it wrong.

The first one I agree with but for the second one in a way yes however they need to make sure their questions have at least reasonably true answers.

 

[BionicMango]

Do we need to know every detail on how nuclear fusion/fission reactors work? Pleaseeee say no.

Not everything but to considerable detail unfortunately

edit: fission only though, for fusion they just look at stars, not human-made fusion reactors which don’t really exist yet

 

[C2H6O]

im pretty sure fusion reactions are only a theoretical thing rn
fission reactors would be good cause you can confuse the roles of the parts, but i found this video quite helpful:

not 100% relevant but the visualisation is useful
skip to 0:58, and everything up to 8:50 is useful, after that you can probably stop watching cause he starts talking about chernobyl but stay if you want to see the reactor working

just rewatched it and something to note is that the graphite moderator is specific to chernobyl, it was one of the design flaws that made it go boom
modern reactors usually use the water to moderate (it still has control properties but this is generally attributed to control rods in hsc), so water can slow down fast neutrons to thermal neutrons to increase reactivity, as well as carry heat away to spin steam turbines

 

[v.tex]

Keep getting cooked in MC

 

[C2H6O]

can someone confirm if answer is C or D? my phys teacher and classmates and me all think its C but HSC answers say D; apparently this is an error?
chatgpt has managed to come up with some reasoning for D being the first galaxies were moving slower and their less redshifted light is only reaching us now bc they're further for some reason, and closer galaxies are newer so move faster and we see as faster now. i still think this reasoning is flawed and really unrealistic for NESA to get students to think this up if its actually D.

 

[BionicMango]

THIS QUESTION!! I remember it.

basically, a would be correct BUT as things get farther away light takes more time to reach us and thus appear to slow down. So d

 

[chikki7]

THIS QUESTION!! I remember it.

basically, a would be correct BUT as things get farther away light takes more time to reach us and thus appear to slow down. So d

idk if this makes sense but is this kinda what u mean? like as you go further out, galaxies end up further away cos the universe expansion speeds up.. so those galaxies take longer time to reach us, which is why theres the decreasing rate of velocity in D as distance is increases

 

[barnyard]

modern reactors usually use the water to moderate

isnt it heavy water (D2O) ??

 

[barnyard]

View attachment 50456
can someone confirm if answer is C or D? my phys teacher and classmates and me all think its C but HSC answers say D; apparently this is an error?
chatgpt has managed to come up with some reasoning for D being the first galaxies were moving slower and their less redshifted light is only reaching us now bc they're further for some reason, and closer galaxies are newer so move faster and we see as faster now. i still think this reasoning is flawed and really unrealistic for NESA to get students to think this up if its actually D.

idk if this makes sense but is this kinda what u mean? like as you go further out, galaxies end up further away cos the universe expansion speeds up.. so those galaxies take longer time to reach us, which is why theres the decreasing rate of velocity in D as distance is increases

velocity increases linearly with distance, which is what hubble found. also, we've found that the ratio of velocity to distance is increasing with TIME (or how i like to think about it, dv/dx is increasing over time) which is why it isnt c. the further distance you go out, the galaxies you see further were formed EARLIER, at a time when the dv/dx was lower, which is why the graph has a lower gradient further!
idk if this will help unless u do ext maths, but i like to think of it as a kind of parametric equation in terms of time. for the present and close past, dv/dx is highest and the galaxies we can see in the close past are those closest to us. so, for small d, the gradient is steeper. for the far past, the galaxies we see in the far past are those which are further since the light takes time to reach us. similarly, in the far past, dv/dx was lower, so for larger d, the gradient is shallower.

 

[C2H6O]

THIS QUESTION!! I remember it.

basically, a would be correct BUT as things get farther away light takes more time to reach us and thus appear to slow down. So d

what the flip im prolly slow but idk what you mean by that
if it takes longer we'll still eventually see it no? the velocity we record is not due to how long it took to see it but how redshifted the light is right? does the time taken have some redshifting effect on the light?
also how are we supposed to account for the acceleration of the expansion of space in the stimulus?

 

[C2H6O]

the further distance you go out, the galaxies you see further were formed EARLIER

can you explain what the reason for this is? ik like the light takes a while to get here but if there were a really old galaxy very close to us we would already see it no?

 

[barnyard]

can you explain what the reason for this is? ik like the light takes a while to get here but if there were a really old galaxy very close to us we would already see it no?

u cant have a really old galaxy close to us, the whole reason we call it an older galaxy is because it's further which is inextricably linked to the time light takes to get here idk. i think it might be bad to think about it in terms of galaxies bc u can get confused w age of formation. like the reason we see the galaxies as older is bc of the light. if a galaxy was close to us, we would see it as it currently is.

 

[chikki7]

velocity increases linearly with distance, which is what hubble found. also, we've found that the ratio of velocity to distance is increasing with TIME (or how i like to think about it, dv/dx is increasing over time) which is why it isnt c. the further distance you go out, the galaxies you see further were formed EARLIER, at a time when the dv/dx was lower, which is why the graph has a lower gradient further!
idk if this will help unless u do ext maths, but i like to think of it as a kind of parametric equation in terms of time. for the present and close past, dv/dx is highest and the galaxies we can see in the close past are those closest to us. so, for small d, the gradient is steeper. for the far past, the galaxies we see in the far past are those which are further since the light takes time to reach us. similarly, in the far past, dv/dx was lower, so for larger d, the gradient is shallower.

i think i get wht u mean, so earlier on the acceleration of the universe was lower, hence galaxies which are further out from us (which existed during this earlier period of lower accel) have lower velocities
and the galaxies nearer to us which are closer to our present experience the greater acceleration of the universe aka have higher vel?

 

[C2H6O]

oh wait hang on it just clicked its not how old the galaxies are its how old the light we're seeing from them is?
the further galaxies are showing us their older light and back in the day expansion was slower, but closer galaxies are showing more recent light which shows them moving faster cause its closer to the present.
eventually when we see the light from older galaxies they will also start moving faster

 

[barnyard]

i think i get wht u mean, so earlier on the acceleration of the universe was lower, hence galaxies which are further out from us (which existed during this earlier period of lower accel) have lower velocities
and the galaxies nearer to us which are closer to our present experience the greater acceleration of the universe aka have higher vel?

yea basically, except i think it's important to note that we dont know about the specifics of the acceleration within the hsc course. ive got no clue if the acceleration is constant or increasing or whatever, the thing that was lower in the early universe is, essentially, the hubble constant (which is the gradient since v=Hd so H=v/d)

dv/dx is different to acceleration, but i think that may be an ex2 maths thing (a=vdv/dx)

 

[v.tex]

Can we simply state x=L.m.lamda/d

 

[Trial&Error]

What in the actual crazy are you guys talking about?? Where did you all learn this?? I've never heard of any of it before, is it in the syllabus? And how are we expected to think of this in the exam? Just whaaaaaaat?!