# Search results

1. ### Finding the potential inside a semiconductor

Homework Statement My question is more about understanding the task itself, not about calculation. I am supposed to use the poisson equation, to derive the potential inside a semiconductor for a barrier with potential height $\phi_B$ and a donator doping with $N1 > N2$. Then I should use...
2. ### Collision of two particles

Homework Statement I am currently solving a problem and I am not sure if it is correct. There are two particles A and B. A has a constant velocity with |\vec{v}| = 3 and starts from y = 30 B has constant acceleration with |\vec{a}| = 0,4 The goal is to find the angle between the...
3. ### I What happens mathematically when a wave function collapses

In Shankars "Principle of Quantum Mechanics" in Chapter 4, page 122, he explains what the "Collapse of the State Vector" means. I get that upon measurement, the wave function can be written as a linear combination of the eigenvectors belonging to a operator which corresponds to the...
4. ### Question regarding an integral

Homework Statement I've got an equation which I need to integrate. However, integrating it and checking with the solutions, I get two different results. I get the same result as using wolfram alpha, but a different result from the book. If I differentiate both results, I get back to the orginal...
5. ### Finding the geodesic equation from a given line element

Homework Statement We've got a line element ds^2 = f(x) du^2 + dx^2 From that we should find the geodesic equation Homework Equations Line Element: ds^2 = dq^j g_{jk} dq^k Geodesic Equation: \ddot{q}^j = -\Gamma_{km}^j \dot{q}^k \dot{q}^m Christoffel Symbol: \Gamma_{km}^j = \frac{g^{jl}}{2}...
6. ### Lagrangian mechanics: Bar connected to a spring

Homework Statement Mass 1 can slide on a vertical rod under the influence of a constant gravitational force and and is connected to the rod via a spring with the spring konstant k and rest length 0. A mass 2 is connected to mass 1 via a rod of length L (forms a 90 degree angel with the first...
7. ### Discrete Lagrangian

Homework Statement In this exercise, we are given a discrete Lagrangian which looks like this: http://imgur.com/TL0P61r. We have to minimize the discrete S with fixed point r_i and r_f and find the the discrete equations of motions. In the second part we should derive a discrete trajectory for...
8. ### 2-D elastic collision circle

Homework Statement Hi there! In this exercise, we are supposed to derive this formula for a 2-D elastic with two different masses: (x-U*v1)^2 + y^2 = (Uv1)^2 (example, two billiard balls), the second mass is at rest. It's a equation which leads to a circle where all of the possible p2' lie...