PeroK's latest activity

Go to the Cosmology forum and click on "Post Thread" https://www.physicsforums.com/forums/cosmology.69/

Can you prove that the arguments about DDWFTTW are between those who understand N3 as you do and those who do not understand it? It...

:welcome:

So, my equation with the deltas was correct. The mistake happened when I switched from ##\Delta## to ##d##. That is something new. In...

We're here to discuss different opinions, not to argue from authority. I apologize if I came off as doing the latter.

Not at all. I'm offering an opinion, not a mandate. I didn't mean to imply that all students are left with these misconceptions, or...

The problem that has arisen here is that if ##\frac{dm}{dt}## is positive for a rocket losing mass, then all the theorems of the...

You have no choice with the derivative: it's positive when a quantity is increasing. You have chosen the opposite convention for...

I suspect the problem is that, because you've taken ##\Delta m## to be positive when the rocket is losing mass, you have...

Okay, the problem must be with your solution to the differential equation.

PS if you want to take ##v_{gas}## as the velocity of the gas relative to the rocket, then you need ##v + v_{gas}## in that equation...

Let's look at this equation in the rest frame of the rocket (##v = 0##). We have: $$(m-\Delta m)(\Delta v)+\Delta m(0-v_{gas})=0$$Which...

I suspect that ##v_{gas}## is the problem. If you use velocities rather than speeds, then you can use a single equation. Moreover, the...

PS try ##v =0## and see what happens.

I can look at this later. In the meantime, what are the possible values of ##v## and ##v_{gas}##?