# Search results

1. ### Examples of units with non-integer exponents

Hi everyone, Would anyone be able to give me a few examples of places where units with non-integer exponents come up? I know of a couple right now: noise voltage density (?) in electronics has units \text{V}/\text{Hz}^\frac{1}{2} and the statcoulomb has equivalent units...
2. ### Optics: Spherical Interface -- Real and Virtual Images

Homework Statement If you have a spherical interface between two different "media" (like air and water), and an object is placed in the one with the lower index of refraction, with the interface being convex toward the object, how can you tell if the image will be real or virtual? Here's a...
3. ### Partial pressure ratio of gases at different altitudes

Homework Statement On a planet not entirely unlike earth, the ratio of the partial pressure of N2 to that of O2 equals 1 at an altitude of 1 km: \frac{p_{\text{N}_2}}{p_{\text{O}_2}} = 1. Assuming that T = 200 K, and the gravitational constant is 5 m/s2, what is the ratio...
4. ### Circuit with capacitors and switch

Homework Statement This is the circuit diagram I am working with: There is actually a switch under C3 that I didn't draw. Initially, the switch was set so that the red dashed line was part of the circuit and the green dashed line was not (so C1, C2, and C3 charged but C4 did not). Then...
5. ### Electric field at a point due to an infinite line charge

Homework Statement Charge is distributed uniformly along an infinite straight line with density λ. Develop the expression for E at the general point P. Homework Equations The electric field at a point P, caused by N point charges Qi, each a distance ri from P, is given by \mathbf{E}...
6. ### Solving for a variable in an equation that involves vectors

Homework Statement I have the equation: \mathbf{F}_{2,1} = \frac{Q_1 Q_2}{4 \pi \varepsilon_0 {r_{2,1}}^2}\hat{r}_{2,1} (standard electric force equation for 2 charges) I know the value of everything except Q2 and have to find it. The vectors each have 3 components. Normally in an...
7. ### Using Relativisitic Units (where c = 1)

Homework Statement It's not really an assigned problem, but it was part of one, and it's a concept that I'm not quite getting. Homework Equations In special relativity, energy can be expressed using the equation E^2 = (pc)^2 + (mc^2)^2, or E = \sqrt{p^2c^2 + m^2c^4}. Apparently...
8. ### Geometry - calculating a distance

Geometry -- calculating a distance Homework Statement I'm trying to calculate the distance from the center of one of these three tangent circles to the center of the entire shape (that is, the center of the "curvy triangular" region between the circles). Each circle has radius R. Here is a...
9. ### (Counting Techniques) Why doesn't this approach work?

It may just be because I probably got only an hour of sleep last night and my thinking skills are not very good, but I'm grading a question on a final exam in discrete math and a lot of stiudents gave an answer that is incorrect, but I can't see why it is incorrect. Homework Statement Given...
10. ### Schools Going to graduate school, but don't know if I really should be

I just graduated last week with a Math/CS degree, and I'm going to graduate school this fall at a different school for CS, working on CS theory and scientific computation (as far as I can tell). The program is really interdisciplinary so I assume I won't be kept locked up in my CS department...
11. ### Really basic circuit-building help?

Hi everyone, Unlike a lot of the other threads and people I've seen here, I'm just playing around with trying to build circuits and have some really basic questions. Before I get any further, is that ok for here as well? (like, is it still considered "electrical engineering") Anyway, I...
12. ### Two-Dimensional Elastic Collision

(This isn't homework help, but it's something that's been on my homework (and other places in my mechanics class)...I don't know if it belongs here or in the homework section. If I'm wrong, sorry -_-) I've had a few questions now in class about a two-dimensional elastic collision between two...
13. ### Better idea to stay in undergrad for 5 years?

So I got to thinking....it might be better for me to delay graduation by a year..or maybe just a semester. But I need advice on this issue (and others) from a lot of different people, and I figured this is one of the places I should ask. I just finished sophomore year and I feel like I'm not...
14. ### My plan for the rest of my undergrad - good?

I'm currently a sophomore with a major in math/cs (single major, not a double major) and I have a plan of what I'm taking for the rest of my time here apart from my degree. I ran it by the general adviser guy and he said it was good, but we really didn't discuss the pros and cons of it, more...