Recent content by Oijl

Homework Statement Bacteria use swimming to seek out food. Imagine that the bacterium is in a region of low food concentration. For the bacterium to profit from swimming to a region with more food, it has to reach there before diffusion of food molecules makes the concentrations in the two...

Homework Statement Consider a protein sphere with a radius of 18Å, and charge Q = -10e, in an aqueous solution of c = 0.05M NaCl at 25 ˚C. We consider the small ions as point charges and use the linear approximation to the Poisson-Boltzmann equation. What is the surface potential of the...

Besides that when I solve for both A' and B' in terms of C and try to evaluate the ratio, I find (k-k1)/(k+k1) which is fine for talking about ratios, but when asked for a probability I want to give a numerical answer.

Not the right section of the forum? Sorry; where should I have posted it? The ratios are the ratios of reflected to initial, and transmitted to initial. This sounds like, then, the probability of the wave to be reflected and the probability of the wave to be transmitted. But if so, why am...

Yay, I got it! I didn't have enough faith in algebra, was my problem. I often don't. Thanks!

Homework Statement Consider particles incident (in one dimension) on a potential energy step with E>U. (That is, particles of total energy E are directed along in one dimension from a region of U=0 to a region of E>U>0.) Apply the boundary conditions for \Psi and d\Psi/dx to find the...

Homework Statement Consider particles incident on a potential energy step with E<U. (That is, a particle with total energy E travels along one dimension where U=0, then crosses, at point x=0 into a region where U>E.) (The particle is incident on the potential energy step from the negative x...

Homework Statement Consider a lamina rotating freely (no torques) about a point O of the lamina. Use Euler's equations to show that the component of \omega in the plane of the lamina has constant magnitude. [Hint: Use the reults of Problems 10.23 and 10.30. According to Problem 10.30, if...

Homework Statement A triangular prism of mass M, whose two ends are equilateral triangles parallel to the xy plane with side 2a, is centered on the origin with its axis on the z axis. Find its moment of inertia for rotation about the z axis. Without doing any integrals write down and explain...

Ta-Da! Thank you, Halls of Ivy, that was kind of you. That's a load off my mind.

Homework Statement Suppose rocket traveler Amelia has a clock made on Earth. She flies to and back from a planet 12 light-years away (as measured from rest with respect to Earth) from Earth at a speed of 0.6c. Every year she sends a signal to Earth. How many signals does Earth receive by...

Homework Statement Find the de Broglie wavelength of an 8 MeV proton. Homework Equations y = h/p where y is the wavelength p = mv K = Eo/sqrt(1-v^2/c^2) where Eo is the rest mass and K is the kinetic energy The Attempt at a Solution I make the assumption that "an 8 MeV proton"...

Homework Statement A particle moves around the surface of an upside-down cone, in a horizontal circular path, in equilibrium. The particle is given a small radial kick. Use the Lagrangian equation for motion (found in a previous section of this problem): m\ddot{r} =...

Homework Statement Consider a system of one generalized coordinate theta, having the following Lagrangian equation of motion: r and b are constants m is mass (1/3)mb^{2}\ddot{\theta} = r(r+b)\theta + r^{2}\theta^{3} + gr\theta And this potential energy (if it matters): U = mg(r+b)...

This is what I'm trying to do: (b) Find the two equations of motion. [Got it.] Interpret the ø equation [\dot{\phi}mr^2 = 0] in terms of the angular momentum l_{z}, and use it to eliminate \dot{\phi} from the r equation in favor of the constant l_{z}. First off, what is l_{z}? That's the...