# Recent content by gsingh2011

1. ### How to think about entropy microstates/macrostates for a gas in a box

I'm trying to relate an analogy from Brian Greene about entropy microstates/macrostates to the real world. In the analogy, you have 100 coins that you flip. The microstate is which particular coins landed heads up. The macrostate is the total number of coins that are heads up. So a low entropy...
2. ### I Is there a reason eigenvalues of operators correspond to measurements?

Given a wave function \Psi which is an eigenstate of a Hermitian operator \hat{Q}, we can measure a definite value of the observable corresponding to \hat{Q}, and the value of this observable is the eigenvalue Q of the eigenstate $$\hat{Q}\Psi = Q\Psi$$ My question is whether it's a postulate...
3. ### Formula for the expected value of a function

The formula for the expected value of a continuous random variable is E(x) = \int_{-\infty}^{\infty} x\cdot f(x). This leads me to believe that the expected value of a function g(x) is E(x) = \int_{-\infty}^{\infty} g(x)\cdot f(g(x)). However, the correct formula is E(x) =...
4. ### Finding the domain of integration in spherical coordinate of a shifted cylinder

So I've done some problems where a sphere intersects with a cylinder and I needed to find the volume of the intersected region using triple integrals. For example, if I needed to find the domain of integration for the intersection of the sphere $$x^2+y^2+z^2=a^2$$ and the cylinder...
5. ### Combinations proof

Thanks, but I'm still not sure what to do from here. I'm not sure how to deal with the sum, I guess. EDIT: I guess I kind of get it now. For the summand, if we keep changing i then we're finding the number of ways to choose 2k elements from n-1 elements by choosing them from each sized set. So...
6. ### Combinations proof

Homework Statement Prove that for any positive integer n, k, $$\binom{n}{2k+1}=\sum_{i=1}^n{\binom{i-1}{k}\binom{n-i}{k}}$$ Homework Equations $$\binom{n}{k}=\frac{n!}{(n-k)!k!}$$ The Attempt at a Solution I'm looking for a starting point. I've been given a hint that says, But I don't know...
7. ### Electric Field for a cylinder without using Gauss's law?

I recently learned how to calculate the field from a cylinder (inside and outside the cylinder) using Gauss's law. I was wondering how I would be able to derive the same formula without using Gauss's law (just for practice). My idea is that you would need to integrate the electric field from...
8. ### Why doesn't this diff eq. have two solutions?

Say you have the diff eq. x'=2x(x-13); x(0)=20. After separating and integrating we get, ln|(x-13)/x|=26t+C From here, we raise e to the power of each side to get rid of the natural log. Does this get rid of the absolute value signs? If so, why? If not, why is there only one solution (as...
9. ### Software for typing programming papers

The syntax is only highlighted in Notepad++, copying it to another program like Word removes the formatting.
10. ### Software for typing programming papers

Just like there's LaTeX for writing math papers and LaTeX editors to parse it, is there anything for writing papers in programming? Specifically a nice way to automatically format code.
11. ### Given a random number from 0-3, return a random number from 0-6

I thought division might be involved, resulting in non-integers. What's the difference? I thought if something was random, the probability for each result would be the same (uniform). I'll try it out, see if I can come up with anything. If anyone else has any other ideas, please share them...
12. ### Why does grounding protect you from electricity?

But I recently saw someone attach a wristband to their hand which was connected to a conducting pad which was connected to ground. After doing this he said it was safe to work with an electronic component sitting on the pad. So if only the electronic component needed to be grounded, he could...
13. ### Given a random number from 0-3, return a random number from 0-6

Well the relationship is that after being given this random number from 0-3, you need to perform mathematical operations (functions such as floor and ceiling are allowed) to arrive at a new number from 0-6. Now if you performed these same steps for the random input number many times, you would...
14. ### Given a random number from 0-3, return a random number from 0-6

This is actually for a program, but the challenging part is really the math. So you're given a number 0, 1, 2, or 3 and the probability of getting each is the same. Now given this random number, I need to output a number 0, 1, 2, 3, 4, 5, or 6 but the probability of getting each number needs to...
15. ### Why does grounding protect you from electricity?

Let's saying you're working with something that has electricity running through it. If you ground yourself by touch something metal, aren't you making it easier for charge to flow through you through the metal, so a greater charge would flow through you? And if you didn't touch something metal...