Recent content by gyorgiy

  1. G

    Faraday's Law and magnetic flux

    Assuming that the field direction is along the axis of the coil (not defined in the question as stated here*), there will be a potential generated in the coil. This is exactly what happens in isolation transformers. The current depends on how the coil is connected. *My assumption is that the...
  2. G

    Motion puzzle: Bird flying between a train and a platform

    It's easy enough to turn this into an explicit formula for each iteration. And easy enough to write a programme or set up a spreadsheet to do the iterations. I doubt that there is a closed-form formula for train distance versus number of trips (other than one that merely embeds the...
  3. G

    Motion puzzle: Bird flying between a train and a platform

    If you wish to iterate, you need to define a cycle that starts from the same place each time - for example the bird arriving back at the platform. In this case, t'2 = 2*t2 - 1 Then each iterative step is finding the value of t(n+1) in: a*t(n+1)^2/2 = 100*(t(n+1)-t'n) and setting t'(n+1) =...
  4. G

    Motion puzzle: Bird flying between a train and a platform

    I suspect that you are overcomplicating? Working backwards, I take it that touching once is the touch when the train is at the platform? Using the numbers backwards we have: Train starts from platform: Dtrain=0 at t=0, so (D in km, t in hours) Dtrain = a*t^2/2, where t is the time in hours...
  5. G

    Motion puzzle: Bird flying between a train and a platform

    The time it takes is D/(V/2), so the deceleration is V/(D/(V/2), or Vinitial^2/(2D)
  6. G

    Motion puzzle: Bird flying between a train and a platform

    That's a very different (and much simpler) problem than the one posed here. The bird flies for 40 hours, fo it flies 4,000-km. And it makes an infinite number of ever-shorter round trips.
  7. G

    Motion puzzle: Bird flying between a train and a platform

    This does not appear to be a normal "homework question". It looks like the result of an attempt to "add just a litle difficulty" to a question. However, in this case it seems to me that this "little extra difficuly" transforms the question from one which has a closed-form solution to one...
  8. G

    Motion puzzle: Bird flying between a train and a platform

    No, the one second delay before each round trip makes the number finite
  9. G

    Chemistry Particle model -- Air passing through a Heat Exchanger

    Hi You are correct - the answer should be the boiling point of nitrogen. I had not appreciated that the -210degC was supposed to be the correct answer. Now I know this, my interpretation (for what it is worth) is that it wasn't just your son who misread the table then it was split between...
  10. G

    A little annoying doubt -- Initial vertical speed of a jumping flea

    The "clue" is in the meaning of "as it leaves the ground": This statement implies two things: Its starting height is zero, and Any force the ground exerts on it lasts for no time after that moment: so the effect on speed will be nil. There are approximations implied in the question which could...
  11. G

    Chemistry Particle model -- Air passing through a Heat Exchanger

    Q4a The information given in the text is incorrect: the boiling point is correct (though I'm not certain I would use that term), but CO2 the triple point (the lowest melting point of CO2) is about -57 degC. So I doubt that the school expects the fully correct answer - below: The CO2 will...
  12. G

    B Is all EM radiation light?

    Agreed - albeit it does depends on the field of work. Neverthelss, the only EM waves I personally have not seen referrenced as "light" are coherent radio frequency emissions below 100-MHz - presumably because there is no known significant source* of these that originally arose from electronic...
  13. G

    B Is all EM radiation light?

    I'll limit myself to physics: It depends on the context and on who is talking. In astronomy, EM radiation can leave its source as viviable light and arrive on Earth as infra-red or even radio waves. Simlarly, radiation can start as x-rays and arrive here as visible light. This makes the...
  14. G

    I Relationship between frequency and power for sound?

    False assumptions make life very difficult. To mininise complexity, I will only describe relationships with gas, pressure and temperature remaining constant. First, let us look at how the energy is stored instantaneously: it transfers between the pressure and the bulk velocity, with the...
Back
Top