Recent content by gyorgiy

Presumably ignore air resistance...

The crucial word in this context is "internal". If you include interactions with external objects, it no longer differs from total energy. However, there are things that will change the internal energy, even if the container is totally rigid and a perfect insulator. First, you are moving the...

Demanding people change passwords in that way is a known risk. Password safes will eventually be cracked. I'm possibly a crackpot, but where it's important, I use an automatically-generated password once and then change a few characters to ones I can remember (and don't allow those to be...

It's most unlikely that PC the PC itself has slowed down unless the the ventillation is clogged or the fan has failed. It's far more likely that the bloat-ware that you don't need is what's causing problems - most likely shortage via filling the memory with junk. .

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...

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...

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) =...

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...

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

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.

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...

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

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...

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...

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...