Recent content by nhmllr

Hi I have to give a presentation on Bogoliubov transformations to my undergrad solid state physics class. The presentation is only supposed to be 15ish minutes long, and defining them alone will take a few minutes. Because of the time constraint, I was wondering if anyone knew of a simple...

How does Fermat's principle of least time (that if light goes from one point to another, any small deviation in the path will result in a path that takes the same time on the first order) follow from Huygen's wave principle? Everyone always says that Fermat's principle can be derived from...

I've heard that before, but I've found them to be pretty helpful and waaaayyy better (and more centralized) at explaining things than most sources. I'm open to suggestion, though. Do you have any better books in mind that would be better for this sort of thing?

I am reading through the Feynman lectures in my spare times (the parts that interest me, anyway). The book and it's explanations are usually high quality, although unfortunately I have come across a very poorly explained part that I cannot understand...

Homework Statement (answer is h * 5 /7) Homework Equations gravitational potential energy = mgh kinetic energy = 1/2 mv2 rotational kinetic energy of sphere = 2/5 mv2 The Attempt at a Solution The gravitation potential energy at the beginning at the top is the same as the kinetic...

I gave the entire problem. No mass was given, and nothing analogous to the spring constant was given. However, I think you can find the ratio of the two, as the period = 2π * sqrt(m/k) = 8. I don't see how that helps, though

I'm sorry, I mis-titled the post originally. The potential graph is not given, only the position vs time graph is given

Ahhhh I see. Both explanations made a lot of sense. Thanks!

Total energy when positions vs time graph is given Homework Statement (answer: -5J) Homework Equations energy initial = energy final The Attempt at a Solution At the crest of each wave, the particle has only potential energy, and at the middle of each wave the particle has only...

Homework Statement Four masses m are arranged at the vertices of a tetrahedron of side length a. What is the gravitational potential energy of this arrangement? (answer is -6Gmm/a) Homework Equations gravitational potential energy = -Gmm/r The Attempt at a Solution One mass is "a"...

...Whoops Thanks

Homework Statement 1. A 0.3 kg apple falls from rest through a height of 40 cm onto a flat surface. Upon impact, the apple comes to rest in 0.1 s, and 4 cm2 of the apple comes into contact with the surface during the impact. What is the average pressure exerted on the apple during the impact...

Right. If ω1*r1 = ω*r, then the kinetic energy stays the same. I still don't understand what the problem is talking about with the "stored energy," because reeling in the tether doesn't affect the energy.

Homework Statement A spaceborne energy storage device consists of two equal masses connected by a tether and rotating about their center of mass. Additional energy is stored by reeling in the tether; no external forces are applied. Initially the device has kinetic energy E and rotates at...

Hmm... that seems negligible though. However, the space between the poles might have an effect on the balls. The large ball is essentially on a flat surface, while small ball has the two poles touching very close to the ball's axis. Now, the rotational kinetic energy of ball is dependent on...