Recent content by meichenl

During lunch today a friend told me that two boats running parallel to one another can be attracted to each other by an effect similar to the Casimir effect. The water waves between the boats are quantized, and there winds up being slightly less pressure from between the boats than from...

hey Turtle, I was snappier than the situation really called for, as well. Glad we're on the same page now.

Physics is not a matter of opinion. I am qualified to answer this question since I have a physics degree from a top school and have taught physics as a private tutor, teaching assistant, and classroom instructor for five years. I spent considerable effort writing that reply, and your...

In previous posts, when I referred to the center of mass, I was talking about the center of mass of the man + cart system. There are two conceptual hurdles to this problem that seem to be troubling you. The first is that we can be very flexible about defining our system when using...

There was a mistake in my previous post. It said the entire system accelerates at 10N/total mass, and that should have been 9N/total mass. In my original scenario, the man and cart would go opposite directions. Then man would be pushed slightly backwards while the cart went forwards. I was...

Hi Rhody, I'll just stick to the ensemble of 2-state systems. In that case, more of them should be at the lower energy level under most conditions. For a given temperature T, we'd have P(low) \propto e^{-E_{low}/T} P(high) \propto e^{-E_{high}/T} using the Boltzmann distribution in...

"If acceleration is constant, then you can derive this using algebra" To be a derivation starting from the fact of constant acceleration, you'd have to prove the equation about average velocity rather than taking it for granted.

Marla, Your equations will be easier to read if you typeset them in LaTeX. Yes, the equation you give is a standing wave. If you start with \Psi(x,t) = A\cos(\omega \left[t-t_0\right]) \sin (k\left[x-x_0\right]) you can just define a new time coordinate and new space coordinate...

Disregarding cosmology, we can still idealize a highest possible temperature for many systems. If the system has a lot of degrees of freedom, each with different possible energy levels, then at absolute zero each degree of freedom should be at the ground state. As we introduce some heat, the...

If an object starts from rest and accelerates, then a plot of its velocity over time is a line, starting at zero with a slope equal to the acceleration. The distance traveled is the area under the velocity vs. time graph. That area under the sloped line is a triangle. The base of the...

the idea of charge is that there are no parts to it. operationally, it works like this: If A and B repel each other. and A and C repel each other. then it turns out B and C repel. If A and B repel and A and C attract then B and C attract If A and B attract. and A and C repel...

The system as a whole will accelerate when there's a force from outside the entire system. Several other posters pointed out that in the case of the man and cart, the man pushes on the ground. Let's say the man pushes on the cart with 10N force. The cart pushes back on the man equally and...

This is a question about simple non-relativistic quantum mechanics in one dimension. If the energy operator is \imath \frac{h}{2\pi}\frac{\partial}{\partial t}, then it would appear to commute with the position operator x. Then, if the energy and position operators commute, I ought to be...

adrian - that's pretty cool. thanks!

adrian, you're right - thank you. mathematica just took a minute or so to do it, and i wasn't very patient. you're also right about the vector interpretation. the argument of the natural log is essentially coming from the law of cosines.