Recent content by cpfoxhunt

Homework Statement This is annoying me because I am so clearly being a muppet somewhere. I need to integrate the vector field (x,-y,z).(vector)ds over the surface of a cyliner x^2 + y^2 < 4 (or equal to) and z is between 0 and 1. The Attempt at a Solution I have to do it both with and...

My brains are clearly falling out of my head, is the answer (8/3)pi? The problem is I don't honestly believe that it is ... using other black arts I get the answer to be 5(pi)/3 but the integration gives 8 ..

Very good point. And yeah, guilty with the swapping the azimuthual with the polar, but thet is apparently the format my exam is going to be in, so I am trying to get used to it. Cheers for the idea, I like that a lot more. Chris

Thanks for the help. So I should just apply divergence theorem then? And integrate over the closed surface of the sphere? How would you guys answer the question? I'm currently tying myself in knots over the whole surface and volume integral topic which is annoying because I understood it a few...

Homework Statement Find the volume of the portion of the sphere x^2 + y^2 + z^2 = 4 for which y>1 (or equal to). Homework Equations I would like to do this using a triple integral. The Attempt at a Solution OK, so I tried integrating the element r^2sin(theta)drd(phi)d(theta)...

Hi, thanks for the reply. I used that relation to work out part a), and now have a single equation Fx = unknown initial ke (v0 dependant) - known final ke. there are three unknowns which I am asked to calculate here. How can I calculate them? Cheers Cpfoxhunt

Homework Statement A ball radius r mass m starts rolling without slipping up a ramp inclinced at an angle phi to the horizontal, and reaches a maximum hight, h. Derive an expression for the angular velocity, omega, that the ball has at the base of the ramp (ignore rolling friction throughout...

Hiya. I'm revising for a classical mechanics first year exam, and the lecture notes on central forces are less then ideal. I'm looking for a fairly simple treatment of the subject with especial regard to circular motion, bound and unbound orbits, binary systems, kepler's laws, distance of...

I am aware of that (and now see why its important). That was what i was trying to get at with my attempt. But I'm still not quite happy - it doesn't explain the unit vector evaluated at (a,b,c), and I feel like I should try to gesture at why D(phi) = del(phi).V ?

Homework Statement Prove that for a 3d space s, defined by a function f(x,y,z) = 0 , a unit vector normal to surface at the point (a,b,c) is given by \nablaf(a,b,c) / modulus of \nablaf(a,b,c) (Apologies for the bad use of latex) Homework Equations None really The Attempt at a Solution I...

Homework Statement I was wondering if I am getting anything like the right answers here to this: 12. A relativistic anti-proton, with total energy 30 GeV, travels 2.5 x i04 light years (2.36 x 1020 m) from the centre of the Milky Way galaxy and collides with a proton in the Earth's...

How did you get to the iinitial photon momentum being -e2? whereas the final momentum is positive? And I still have a p3 i.e. the momentum of the electron after the collision floating around. Any ideas?

Homework Statement This is the last problem I'll trouble you guys with, I'm just completely stuck on it. Here it is. In the jet of a quasar, an ultr&relativistic electron collides head-on with a very low energy photon of the cosmic microwave background. No new particles are created...

Homework Statement This is a really easy one, goodness only knows why I can't think of how to do it, here goes " Explain why a photon in free space cannot turn into an electron-positron pair." Homework Equations I assume E^2- P^2 = 0 will be of some help The Attempt at a...

That's 4 vectors? I'd call that the invarient quantity first for the system and then for the individual particules. I'm a abit confused though - is that enough information to eliminate all the unknowns? And just for completeness, are there any other simple ways of doing the problem along the...