Recent content by ppy

Hi, I have attached a file. I am stuck on question 1 on how to find Noether's constant. The solutions are provided however I do not see what they have done. It states that η^{x}=1 and η^{y}=-1 I do not understand how we know this. I can see that \xi=0 because else the -x^{2}-y^{2}-2xy term...

Hi, I know that for the electric displacement vector field \oint D.dS=\sum Q_{c} does this mean that I can just use a Gaussian surface to explain why the displacement vector field for a sphere is radial or not without having to talk about the electric field. If not what is the reasoning to...

are you saying I just use 3NkT/m and sub in 500k? There is no extra calculation that what was done in part (a)?

So you are saying to use the result from (a) but we do not know the mass of the particles?

The rms speed for a particle in a gas can be calculated using the formulae: u_{rms}=\sqrt{\int(u^{2}n(u)du)/N} a) Use the formulae and the expression for n(u): n(u)=(\frac{2^{1/2}N}{\pi^{1/2}})(\frac{m}{k_{B}T})^{3/2}u^{2}exp(-\frac{mu^{2}}{2k_{B}T}) To estimate the rms speed of Ne...

Thankyou for the reply I thought for a) the electric fields in the x direction will cancel but the electric field for the y direction will be \frac{qsin(45)}{4\piε_{0}a^{2}}=\frac{\sqrt{2}q}{4\piε_{0}a^{2}} for one point charge and therefore twice this for 2 point charges as the y components...

so is the resultant electric field \frac{\sqrt{2}q}{4\piε_{0}a^{2}} in the perpendicular direction to the base and therefore the magnitude of the torque is pEsinθ=\frac{pq}{4\piε_{0}a^{2}} ? What about for b) ?

2 particles of charge q are placed at 2 vertices of an equilateral triangle of side a. An electric dipole is placed at the third vertex with its dipole moment orientated parallel to the opposite side of the triangle. a) Determine the magnitude of the torque on the dipole due to the electric...

Thanks. I've got there now !

The integral started out as a triple volume integral. The part mentioned is the final part of the triple integral. I have tried x=sinu and still got nowhere. Is it a simple substitution or do I have to integrate by parts as well ? Thanks

Hi, I was attempting a volume integral question out of a book. I know what the final answer is and what integral i am supposed to work out but I do not know how I am supposed to solve it. I have tried different ways such as integration by substitution and integration by parts but I do not seem...

Hi yes the 2 should be a squared. This question is worth 6 marks. What would you have to do to get so many marks other than writing what you suggested?

Hi, N atoms are arranged to lie on a simple cubic crystal lattice. Then M of these atoms are moved from their lattice sites to lie at the interstices of the lattice, that is points which lie centrally between the lattice sites. Assume that the atoms are placed in the interstices in a way...

yes I meant if you apply a force to the stick above its centre of mass. If the stick has a force applied at this point does it still rotate about its centre of mass and will the centre of mass still fall vertically? Also another question, if a stick is placed vertically on frictionless ice as...

A thin stick of length L is balanced vertically on frictionless ice. What happens to the motion of the centre of mass if it gets a big push above the centre of mass of the stick? Does the centre of mass move? If so how do you work it out? This is more of an extra question I thought of when...