Recent content by ngc1333

Got it.

Interesting. I wonder what happened to that post. I tried to edit a mistake (the line after the "From conservation of energy" has an extra 1/2 that I tried to get rid of). I guess I screwed something up editing it.

Do you know calculus? I swear I posted something here last night, but it's gone now. If you know calculus I'll post it again. If not, I don't see how you can solve the problem.

Just to be clear, I'm using the 4th ed of HRK, simply titled Physics. Halliday, Resnick, and Walker wrote a newer book called Fundamentals of Physics that I am not familiar with. Chapter 6 of HRK pretty much has what you are looking for. In section 6.4 they show you the "calculus way" to derive...

It all comes from the definitions of position and velocity: a = dv/dt and v = dx/dt. It's more useful to write in differential form: dv = adt dx = vdt For constant acceleration you can integrate the first equation to get: v = at + const. Plugging in t = 0 gives you the...

This is a true statement: if 48/2(9+3) = 2, then 24=0.1666 ... The statement A implies B is true unless A is true and B is false. In this case, A is not true. You cannot conclude from this (true) statement that the conclusion, 24=0.1666 is true.

Are you certain that air pollution was "wrong"? The only alternative I can see would have been to avoid the industrial revolution. That's true, but we could still do a lot more. We could shut down all non-essential industries to reduce our power needs, outlaw non-essential driving . . ...

Air pollution kills millions of people every year, just to put things in prospective.

Not sure about the first one. The electric field line would point straight up at that point. A negative charge would be accelerated straight down. Then it would of course move to the right as well, but the problem asked for the initial motion.

I'm pretty sure he is talking about this: http://www.nytimes.com/2010/07/13/science/13gravity.html" Yes.