# Recent content by Haye

1. ### Temperature profile around heat source

Homework Statement A point source in water provides 10 W of heat for 10 seconds, and is then shut off. The surrounding water has a temperature of 20 °C. Provide the temperature profile as a function of distance r and time t. Homework Equations The Attempt at a Solution If it...
2. ### Moment and force calculation for cantilever beam

OK, thank you! I finally understand the problem. I really appreciate the help!
3. ### Moment and force calculation for cantilever beam

I did draw the free body diagram, but I have a lot of trouble understanding the concept of moment. There should be a reaction moment at the wall even without P I just realized; this reaction moment has to cancel PL. But I find it really hard to see what I need to do with the moment M. Would...
4. ### Moment and force calculation for cantilever beam

Homework Statement A cantilever beam (prismatic, rectangular cross section) is loaded at the tip by a force P and at half its length L by a moment M. a. Calculate the reaction force and moment. b. Draw the shear force and bending moment diagrams Homework Equations ∑F=0; ∑M=0 The...
5. ### Finding initial speed of ball

There is no angle given, so you shouldn't assume any angle. You can calculate vx and vy without using the angle. If you want to know the angle afterwards, you can calculate it from vx and vy.
6. ### Circuits question

Electrons are negatively charged, and flow in the opposite direction of the current.
7. ### Finding initial speed of ball

Yes, you indeed made a wrong assumption on the angle. If you take a good look at the values given, you should be able to calculate vx without much trouble. Then you only need to calculate vy.
8. ### Electric force in an electric field.

I am not sure how to explain it properly, but the third point charge can't really affect itself, can it. So you just calculate the electric field at that point as if it wasn't there.
9. ### Dimension of Hilbert space (quantum mechanics)

Ah, that makes much more sense, J=L+S ofcourse. I understand it know, thank you so much for your help (:
10. ### Determining charge of q and the spring coated with metal?

Your method for a is correct, you just forgot to write the 1/r². For question b, you just need to think about what happens to the charges. What changes when you go from an insulated spring to a conducting one?
11. ### Electric force in an electric field.

You know how to calculate the force between two charges. You can just calculate the force that act on the last charge from the first one, and then the force it feels from the second one. Then you can just add up the two forces. Just make sure you know you're adding up vectors.
12. ### Dimension of Hilbert space (quantum mechanics)

s should be 1/2, sorry for that. Thanks for pointing me in the right direction, I'm a lot closer to the answer now (I think so, atleast). If I am correct, the 'spin-angle functions' would give me the number of bases vector, and thus the dimension of the Hilbert-space. This is dependent on...
13. ### Dimension of Hilbert space (quantum mechanics)

Homework Statement Consider the states with the quantum numbers n = l = 1 and s = 1/2 Let J = L + S What is the dimension of the Hilbert space to describe all states with these quantum numbers? Homework Equations The Attempt at a Solution I believe the dimension of the Hilbert...
14. ### Show ψ(x,t) = f(x-at) + g(x+at) satisfies the wave equation

Your f(x-at), set: y=f(u) u=x-at Chain rule: dy/dx=dy/du*du/dx dy/dx=f'(u)*1 This is how you can differentiate your function, same goes for differentiating to t. If all goes well, the f'(u) should cancel out. Also, you have the wrong wave equation there; both differentials are with...
15. ### Question regarding charges on a hollow sphere

Homework Statement I have a hollow conducting sphere with a charge on it, and I'm looking at the static situation. Where are the charges located? Homework Equations Gauss' Law The Attempt at a Solution A static situation, so no electric field inside the sphere, or charges would move...