Welcome, Guest. Please login or register.

July 16, 2019, 12:26:43 pm

Author Topic: Newton's Laws and probably more questions  (Read 4412 times)  Share 

0 Members and 1 Guest are viewing this topic.

xZero

  • Victorian
  • Forum Leader
  • ****
  • Posts: 898
  • Respect: +68
Re: Newton's Laws and probably more questions
« Reply #30 on: November 03, 2011, 04:50:46 pm »
0
Why does a pool appear shallower if you look at the bottom from directly above? what does the speed of light have to do with this? If you're looking from directly above, wouldn't there only be a change in speed and no change in angle?

I think this diagram answers your question, the observed depth Y is less than the actual depth X but this doesnt happen when you're looking straight down the pool from above.
2009: Chinese SLA
2010: English, Maths method[45,A+ A+ A+], Specialist maths[44,A+,A,A+], Physics[40,A,A+,A+], Psychology Atar:94.75
2011-2015: Bachelor of Aerospace Engineering/Science @ Monash

Methods/Spesh/Physics tuition

#1procrastinator

  • Guest
Re: Newton's Laws and probably more questions
« Reply #31 on: November 03, 2011, 04:57:29 pm »
0
yep, thanks for putting up with these questions lol

ah that makes a bit more sense. so, an ocean wave - that would be an elastic medium? i think in the book it said none of the molecules that crash on the beach would have been at the source of the wave so there's no transfer of matter

I googled 'elastic medium' - didn't get any helpful results :p

---

About the units, that' was a question from the alternative energy topic (something like that). I don't remember it exactly but basically there's a solar panel and you had to work out the rate of energy absorbed per sqm

So 10J per square metre per second is 10J/m^2/s and when you simplify it mathematically , you get 10J/m^2 s which reads 10J per square metre second which don't make sense. I guess basically what I wanted to know if it's still considered J per metre squared per second or does metre squared second mean the same thing?




@xZero - what about when you're looking from directly above? i can't find anything in my textbook about that but in the handouts, it says  a pool appears shallower when looking from directly above (no refraction)

Lasercookie

  • Honorary Moderator
  • ATAR Notes Legend
  • *******
  • Posts: 3174
  • Respect: +321
Re: Newton's Laws and probably more questions
« Reply #32 on: November 03, 2011, 05:09:26 pm »
0
Quote
I googled 'elastic medium' - didn't get any helpful results :p
Yeah, I found that as well.

Quote
So 10J per square metre per second is 10J/m^2/s and when you simplify it mathematically , you get 10J/m^2 s
not

Quote
@xZero - what about when you're looking from directly above? i can't find anything in my textbook about that but in the handouts, it says  a pool appears shallower when looking from directly above (no refraction)
Snell's law was it? If you plug in the angle 0 for incident angle, what is the refracted angle? It's 0 is it not. (I hope I used the correct formula).

http://en.wikipedia.org/wiki/Snell's_law

I used the one off Wikipedia, if I remember correctly, angle 1 is incident, angle 2 is refracted. n2/n1 = 1.33 for air into water (rounded off air to 1). If I did mix up my angles, either way, they will both be zero. 

#1procrastinator

  • Guest
Re: Newton's Laws and probably more questions
« Reply #33 on: November 04, 2011, 12:05:25 pm »
0
So you treat the as a fraction and not and and together? This is what I did:



Would everything together be



?

Lasercookie

  • Honorary Moderator
  • ATAR Notes Legend
  • *******
  • Posts: 3174
  • Respect: +321
Re: Newton's Laws and probably more questions
« Reply #34 on: November 04, 2011, 04:39:12 pm »
0
So you treat the as a fraction and not and and together? This is what I did:



Would everything together be



?
Oh yes, you're (almost) correct, I see my mistake.

I assumed: , but since it's Rate of "energy absorbed per sqm", it would be:
which simplifies to: (this is what you had)
This further simplifies to:
(Joules per sq. metre per second)

Note that (I'm guessing you simply forgot the type up the -1 at the end in that post)

A bit of beating around the bush, but I think I can confirm that

#1procrastinator

  • Guest
Re: Newton's Laws and probably more questions
« Reply #35 on: November 04, 2011, 05:38:19 pm »
0
That was based on your last post :p

so does that read 'joules per metre squared per second', or 'joules per metre squared second' (what didn't make sense to me, unless it means the same thing...i want to make sure i got this lol)

xZero

  • Victorian
  • Forum Leader
  • ****
  • Posts: 898
  • Respect: +68
Re: Newton's Laws and probably more questions
« Reply #36 on: November 04, 2011, 05:53:10 pm »
0
they are different, joules per metre squared per second is and joules per metre squared second is
2009: Chinese SLA
2010: English, Maths method[45,A+ A+ A+], Specialist maths[44,A+,A,A+], Physics[40,A,A+,A+], Psychology Atar:94.75
2011-2015: Bachelor of Aerospace Engineering/Science @ Monash

Methods/Spesh/Physics tuition

Lasercookie

  • Honorary Moderator
  • ATAR Notes Legend
  • *******
  • Posts: 3174
  • Respect: +321
Re: Newton's Laws and probably more questions
« Reply #37 on: November 04, 2011, 05:57:00 pm »
0
they are different, joules per metre squared per second is and joules per metre squared second is
Hmm, well that makes a lot more sense.

I am not entirely sure what I've been doing wrong though (somewhere in my mathematics probably, I'm guessing probably with my initial assumptions).

#1procrastinator

  • Guest
Re: Newton's Laws and probably more questions
« Reply #38 on: November 04, 2011, 07:10:52 pm »
0
they are different, joules per metre squared per second is and joules per metre squared second is

So over ...how did you know?

#1procrastinator

  • Guest
Re: Newton's Laws and probably more questions
« Reply #39 on: November 10, 2011, 05:32:57 pm »
0
How come it isn't J/m^2 and s/1?

And I just noticed you mention kg/s^3 laseredd, that makes no sense to me haha (i think i know how the calculator got that though)

If a jet fires a missile, it pushes back against it right (if not released first), but what if the missile was fired at a low acceleration so it gradually increased it's velocity to match the aircraft's before being released, would this act as a boost for the jet? There would be no push back, yes?


EDIT: How would one go abut deriving the work formula?
« Last Edit: November 10, 2011, 05:36:39 pm by #1procrastinator »

xZero

  • Victorian
  • Forum Leader
  • ****
  • Posts: 898
  • Respect: +68
Re: Newton's Laws and probably more questions
« Reply #40 on: November 10, 2011, 05:43:21 pm »
0
they are different, joules per metre squared per second is and joules per metre squared second is

So over ...how did you know?
replace per with /
joules per metre squared per second = joules/m^2/s = Js/m^2

joules per metre squared second = j/m^2s

If a jet fires a missile, it pushes back against it right (if not released first), but what if the missile was fired at a low acceleration so it gradually increased it's velocity to match the aircraft's before being released, would this act as a boost for the jet? There would be no push back, yes?
jet usually release missile before it accelerates, letting it accelerate before release is just wasting fuel, prob run out of juice before you can fire it
2009: Chinese SLA
2010: English, Maths method[45,A+ A+ A+], Specialist maths[44,A+,A,A+], Physics[40,A,A+,A+], Psychology Atar:94.75
2011-2015: Bachelor of Aerospace Engineering/Science @ Monash

Methods/Spesh/Physics tuition

#1procrastinator

  • Guest
Re: Newton's Laws and probably more questions
« Reply #41 on: November 10, 2011, 05:48:00 pm »
0
joules/m^2/s , i don't get why m^2 and second are together in a fraction and not joules and m^2


hypothetically :p

it's the acceleration that pushes it back though, right? if it was increasing velocity slowly, there would be no (or very little) push back?

xZero

  • Victorian
  • Forum Leader
  • ****
  • Posts: 898
  • Respect: +68
Re: Newton's Laws and probably more questions
« Reply #42 on: November 10, 2011, 05:59:30 pm »
0
idk, joules per metre squared per second is just a badly phrased sentence, its like the divide sign argument on facebook. I interprete it as joules/m^2/s=Js/m^2
2009: Chinese SLA
2010: English, Maths method[45,A+ A+ A+], Specialist maths[44,A+,A,A+], Physics[40,A,A+,A+], Psychology Atar:94.75
2011-2015: Bachelor of Aerospace Engineering/Science @ Monash

Methods/Spesh/Physics tuition