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  1. R

    Falling Ladder

    you mean can a ladder fall from such a height and be expected to land in the ground? i dont think so.
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    What exactly perspective is?

    the reason why things look bigger as you get closer is simple and it's just down to geometry. the angle an object subtends to your eye tells you how much of your vision it takes up (not sure why the inverse square law was being mentioned) the angle subtended can be found with simple, rough...
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    Differentiate the given function using implicit.

    youve answered the question - youve differentiated what you were given. if you want to find dy/dx explicitly, you can try factorizing to get there.
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    E=m*c 2 or

    edit: oops, ignore this
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    Angular tilt from a x/y angles

    would you care to mark on the angles/lengths you know on a diagram? im really not able to follow a description that well.
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    What is energy?

    haha your example is hilarious :rofl: i thought you handled it extremely well when somebody trying to be philosophical called you pedantic. you are much more patient than me! :tongue:
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    Combining Magnetic fields together

    a magnetic field is basically a vector field. every point has a vector associated with it which tells you what force the field exerts on the particle and the direction of this force. you want to know what happens when you add vector fields - im sure you know what happens when you add vectors...
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    Angular tilt from a x/y angles

    im not really clear on what you mean? [PLAIN]http://img193.imageshack.us/img193/8507/wedgef.jpg [Broken] you mean moving from one red point to another? could you tell us all the information you know? i expect you can do this question either with geometry or energy
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    Black Holes : Zero Volume, Infinite Density

    well, black holes dont have zero volume. google the schwarzchild radius.
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    Is the speed of sound relative?

    what are you talking about? if you move towards a source of sound at speed v, the speed of the sound waves relative to you is (340+v)m/s contrast this with light where if you move towards a torch with velocity v, the speed of the light waves relative to you is c m/s, the speed of light. the...
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    Aircraft propulsion technology

    have you seen newton's second law written in the form f=d(mv)/dt ? edit: oops, dead thread..
  12. R

    Is the speed of sound relative?

    not at all, the argument itself is banned. you would be told off if you posted a tonne of scientific journals supporting global warming. also opinions cant be proven and QED is a pretty ridiculous thing to say there.
  13. R

    Is the speed of sound relative?

    speed of sound depends on the density means its related to the density. the OP asked if the speed of sound was relative ie relative to the motion of the observer
  14. R

    Is the speed of sound relative?

    thats not what the OP asked. youre explaining why the speed of sound is related to density. PS banned topic of discussion
  15. R

    Math Question

    interesting - a very similar question came up in a 1st year cambridge physics paper (http://www-teach.phy.cam.ac.uk/dms/dms_getFile.php?node=5735")
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    Non-symmetric nature of the Doppler Effect with sound

    yeah, i dont know why i didnt do that.. i get 1117.6Hz
  17. R

    Theoretical physicist

    take your a levels seriously: do well in maths and physics. apply for a theoretical/mathematical physics degree. get in, study hard there and see if youve got what it takes.
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    Non-symmetric nature of the Doppler Effect with sound

    :tongue: thought so.. so the doppler shift is basically the change in the measurement made in the measurement-taker's rest frame? if you think about the person ("me") who hears the sound, it clears it up especially if i consider "my" rest frame in each scenario a) im stationary (this is my...
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    Non-symmetric nature of the Doppler Effect with sound

    when you say the medium is moving, do you mean the medium is moving in the observer's frame of reference?
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    Newtonian derivation of Scwarzchild radius

    heh, cant wait to study it all properly. thanks :)
  21. R

    Newtonian derivation of Scwarzchild radius

    yeah, this seems much too complicated to explain to a level students ^^ :tongue:
  22. R

    Newtonian derivation of Scwarzchild radius

    can anyone say why the derivation works? my teacher went through it in class and sort of said "don't question it" (which i hate) but it's still annoying me now even though it's a few weeks since i finished college. KE = GPE 0.5mv² = GMm/r r=2GM/v² and then if the escape velocity is the...
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    Advice about volunteering abroad

    Hi, I'm 18 and have just completed my A levels. I will be studying physical natural sciences at uni if I've got the grades in my a levels (I'm pretty sure I have) I would like to volunteer teaching high school level maths and/or physics in quite a deprived country (somewhere in Africa...
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    Revising simple lenses - magnified, and diminished images

    Basically, I'm trying to revise lenses and the one thing I never really understood was how to tell whether an image is magnified or diminished. http://store.aqa.org.uk/qual/gce/pdf/AQA-2450-W-TRB-OGA.PDF pages 6 and 7 has the diagrams to show what I mean I can do the geometry of an object...
  25. R

    Proof that the sum of a number's digits is a multiple of 9 iff it is divisible by 9

    okay thanks :) i know its not rigourous but i think its watertight enough for the level im working at
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    Proof that the sum of a number's digits is a multiple of 9 iff it is divisible by 9

    Homework Statement prove that the sum of a number's digits is a multiple of 9 if and only if it is divisible by 9 Homework Equations none that i can think of The Attempt at a Solution say any real integer can be written as: anan-1...a2a1a0 where a0 is the units, a1 is the tens...
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    Eigenvectors - why must det(A-λI)=0?

    so if Bu=0 then there can be 2 solutions: u=0 (uninteresting) or B=0 (also uninteresting) if B is invertible, then B-1Bu=B-10 so u=B-10=0 which is equivalent to before i just dont see the logic that says that that says that interesting answers must exist if B-1 doesnt exist can it not be...
  28. R

    Eigenvectors - why must det(A-λI)=0?

    sorry for this silly question.. B= A-λI u is an eigenvector but what is v?
  29. R

    Eigenvectors - why must det(A-λI)=0?

    okay, thanks for that. is it weird for my maths class to be learning about eigenvectors when we have no clue about null spaces? it seems like the Bu=0 where B,u ≠ 0 problem can only be explained with null spaces so it seems odd to try and learn eigenvectors before learning about null spaces :S
  30. R

    Eigenvectors - why must det(A-λI)=0?

    if we say that an eigenvector u is a vector whose direction is unchanged by the matrix transformation A: Au=λu=λIu rearranging: Au - λIu = 0 u(A-λI)=0 we know the u=0 is obviously a solution. and i also appreciate that if A-λI=0 then A=λI which is just a scalar multiplied by the identity so is...
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