HSC Physics Question Thread

[jamonwindeyer]

Hi! I'm having trouble visualising what Black body radiation is. (like what it physically is). Are they just normal objects that can absorb all radiations?
Also the graph that goes with it, intensity VS wavelength. I'm not completely understanding what it all means.
Basically the whole concept of black body radiation is confusing.:/
Thanks

Hey! I actually did a big explanation of the black body curves not long ago, you can find that here!

As for what a black body actually IS, it's a perfect absorber and emitter of radiation - Nothing bounces off, if anything hits it, it is absorbed into the body. Note that a perfect black body is a theoretical construct, all objects have some amount of incoming radiation that is reflected

[crazycodpro]

please help 

[jamonwindeyer]

please help 

Hey! This is a weird one, but force is just mass times acceleration due to gravity:



I think the dimensions are perhaps just red herrings?

[gilliesb18]

Can someone help me understand just the start of the waves topic??? How do i differentiate between louder sound and quieter on a graph?
Also can someone give me an example of one dimensional, two dimensional, and three dimensional waves?
Thanks in advance.
B...

[jamonwindeyer]

Can someone help me understand just the start of the waves topic??? How do i differentiate between louder sound and quieter on a graph?
Also can someone give me an example of one dimensional, two dimensional, and three dimensional waves?
Thanks in advance.
B...

Hey! Louder sound means more energy in the wave, which corresponds to greater peaks in a transverse representation of your sound - See below!



As for 1/2/3 dimensional waves, hopefully these examples suit!

1 Dimensional Sending a pulse along a spring/slinky (single dimension of movement, along the slinky)
2 Dimensional: Earthquake waves along the earth's surface (two dimensions, up/down and left/right)
3 Dimensional: Sound waves moving in three-dimensional space

[gilliesb18]

Ok thanks!!! That's great....
Hey I have a really really strange question but just recently at school we have been having this discussion about the Bermuda Triangle and someone said something about a Physics law being the source the problems. Is this right?? Or could it just be another theory?
Just thought i'd ask on here cause there's heaps of smarties hanging out on here!!!!

[jakesilove]

Ok thanks!!! That's great....
Hey I have a really really strange question but just recently at school we have been having this discussion about the Bermuda Triangle and someone said something about a Physics law being the source the problems. Is this right?? Or could it just be another theory?
Just thought i'd ask on here cause there's heaps of smarties hanging out on here!!!!

As far as I can tell, there's nothing Physics related going on there! Just a lot of confirmation bias, in a high-use shipping zone.

[gilliesb18]

Ok sure!!! Thanks for confirming that!

[jamonwindeyer]

Ok sure!!! Thanks for confirming that!

In reality, Jake is the cause of the Bermuda Triangle drama. He lives there and shoot Physics lasers at boats that get too close

[gilliesb18]

Hahaha sure I thought that!!!!

[Jyrgal]

hey! my friend was just asking this to me the other day, if spaceship #1 travelling at 0.8c passes spaceship #2 travelling at 0.9c, what would spaceship #1 see spaceship#2 going at?

another question: from earth's perspective, if a rocket accelerates from 0.7c to 0.8c and next to it another rocket accelerates from 0.8c to 0.9c, while both rockets have same thrust, would the observer from earth see the rockets accelerate for the same amount of time?

thanks

[jamonwindeyer]

hey! my friend was just asking this to me the other day, if spaceship #1 travelling at 0.8c passes spaceship #2 travelling at 0.9c, what would spaceship #1 see spaceship#2 going at?

another question: from earth's perspective, if a rocket accelerates from 0.7c to 0.8c and next to it another rocket accelerates from 0.8c to 0.9c, while both rockets have same thrust, would the observer from earth see the rockets accelerate for the same amount of time?

thanks

Hey! You are asking some hardcore questions there, they both feature relativistic relative velocities. It's the basic idea of relative velocities (throw a ball at 10 kilometres an hour out of a car going 20 kilometres an hour, to a stationary observer those are added to give 30), but you need to add in the effects of time dilation and length contraction here's some info on it, but it goes way beyond what you need for the HSC, and way beyond what I've touched in my studies (Jake has done it, he might be able to help!)

For your second question, again I'm honestly not sure, but I think the faster rocket would be seen to accelerate for longer due to increased effects of time dilation? That would be my (very uncertain) guess - These are really cool questions to be asking!!

[jakesilove]

hey! my friend was just asking this to me the other day, if spaceship #1 travelling at 0.8c passes spaceship #2 travelling at 0.9c, what would spaceship #1 see spaceship#2 going at?

another question: from earth's perspective, if a rocket accelerates from 0.7c to 0.8c and next to it another rocket accelerates from 0.8c to 0.9c, while both rockets have same thrust, would the observer from earth see the rockets accelerate for the same amount of time?

thanks

All of this comes down to Lorentz transformations, which are NOT in the syllabus for some reason. For instance, I think that first question is totally easy, just as straight forward as the usual relativity question, IF YOU WERE GIVEN THE FORMULA! However, you're not, so for now I would just focus on what is actually assessable.

Re your second question; no idea, Relativity doesn't really like acceleration, the maths gets too tough.

[winstondarmawan]

Hello! My friend and I have been arguing about the answer to this question.
Please sort it out!
Thanks in advance.
https://scontent-sjc2-1.xx.fbcdn.net/v/t34.0-12/18601262_1973433546221520_1725643649_n.png?oh=b1bbc6a1c159ab8b0cb10f13786a43d0&oe=59230D4C

[jamonwindeyer]

Hello! My friend and I have been arguing about the answer to this question.
Please sort it out!
Thanks in advance.
https://scontent-sjc2-1.xx.fbcdn.net/v/t34.0-12/18601262_1973433546221520_1725643649_n.png?oh=b1bbc6a1c159ab8b0cb10f13786a43d0&oe=59230D4C

Ahaha hey! I think towards 4 at the bottom, towards 1 at the top. If you consider the bottom, we have a N pole moving towards the bottom - So we want to push the N away (Lenz's Law). So, by the right hand grip rule, we want to induce a counter clockwise current - That generates a north pole equivalent field directed towards the magnet to oppose its motion. Then the top is just the opposite - We want a north pole directed downwards to try and bring the S pole back up. Therefore, clockwise current

This was just a quick run through - But does it make sense? (who won the argument? Ahaha)