Recent content by lagwagon555

Homework Statement Consider the intersection of two surfaces: an elliptic paraboloid z = x2 + 2x + 4y2 and a right circular cylinder x2 + y2 = 1. Use Lagrange multipliers to find the highest and lowest points on the curve of intersection The Attempt at a Solution L = x^2 + 2x + 4y^2...

Ah right I see, thanks a lot for clarifying that. I'm taking a senior level maths paper after 2 years of not doing maths, so I keep slipping up on things like that. Thanks again :)

Homework Statement Find the partial derivative with respect to x of sin(xyz - 1) Homework Equations None needed. The Attempt at a Solution I took the answer to be yz*cos(xyz - 1), but wolfram alpha is giving me yz*cos(1 - xyz). Anyone know what's going on here? Thanks!

Homework Statement http://img33.imageshack.us/img33/1147/question1x.jpg Homework Equations V = IR, Sum of currents at junction = 0. The Attempt at a Solution Just doing some exam revision, and found this one in my notes. I'm not really sure how to go about it. Using Kirchhoffs rules, you...

The way it was actually written was BTA, so I think it made a point of showing that it wasn't (AB)T. So I'm thinking that the answer is that it can't be computed? Thanks for the quick reply! EDIT: ooooooooooh. Ooops. How embarassing. Of course it makes a difference when B comes first. Argh!

Homework Statement Find A*B^T, where A= 2 1 5 3 And B= 1 -1 1 -1 1 1 Homework Equations n/a The Attempt at a Solution The problem is, is that if I get the transpose of B, I will end up with a 3x2 matrix. Isn't this impossible to multiply by a 2x2...

Homework Statement A beam of light of 300nm is shone at a metal surface of work function 2.25eV. The power of the light striking each square centimeter is 1 microW. A total of 3cm^2 is illuminated by the beam. If each photon caused an electron to be ejected, what current is produced...

Homework Statement Microscopes are inherently limited by the wavelength of the light used. How much smaller (in order of magnitude) can we “see” using an electron microscope whose electrons have been accelerated through a potential difference of 50 000 V than using red light (500 nm)...

Absolutely brilliant. I haven't seen that equation yet, so I'll have to look it up to understand it, but it sure as heck works! Thanks for your time, hugely appreciated.

Homework Statement The element N has 7 electrons and 7 protons in the atom. An ion of N has all the electrons removed except 1, so it resembles a hydrogen atom with a nuclear charge of +7 e. E1(Hydrogen)= -13.6eV, r1(Hydrogen)= 5.29x10^-11m. k = 8.99x10^9 e = 1.6x10^-19 What is...

Haha, not my brightest moment ever. Thanks for clearing that up!

Homework Statement Solve the equation x = (1.66x10^28)/(sin^3(45)) Homework Equations n/a The Attempt at a Solution My attempt is really non existent, since I haven't had to work with sin^3 before, I haven't even seen it before this assignment. Basiclly I'm working out the mass...

Hi all, I'm working on a problem where I have to find the time it takes for a planet to form from a protoplanetary disk, using the equation: t = \frac {3}{A}M^{1/3} Where A= ( \frac {(1+2\beta)\sigma}{P}) (\frac {3\pi^2}{4\rho_m})^{2/3} However, I'm not sure which units the...

Well if you're a college student, you will be able to tackle Astrophysics in a Nutshell. I haven't encountered any multivariable calculus yet, so the book (if it does at all) makes very minimal use of it. If you are in college, and have a decent maths textbook, you will be absolutely fine. You...

As said above, you should really search the forums, there are heaps of discussions like these. For my introductory astrophysics course, I'm using Astrophysics in a Nutshell by Moaz. It seems to cover a lot for only a couple of hundred pages, and I love the way it is written. However, I'd only...