Recent content by Engels

Homework Statement We have the force field F= (-4y+yx^2)i - (xy^2)j. Find the simple closed curve in which the work produced by the Force field is maximum Homework Equations vector calculus( curved intergrals second type, green stoke's gauss theorems...)

i mean the velocity for t=1 which is r'(1)= 2i-j+4k The r(t) in my previous post is the position vector from the start (0,0) is the any reason for not the r'(t) or r'(1) to be the objects velocity?

Homework Statement An object moves according to this : r(t)= (1+t^2)i + (1-t)j + (t+t^3)k How fast does it moves far from O(0,0) for t=1? Is this velocity the same with the object's velocity? The Attempt at a Solution I can't understand the second part

Curl div... Homework Statement f is a scalar field. What does div(f) curl(f) rotgrad(f) divgrad(f) stand for? I need to know if a scalar field can have the meanings of roration and diverge like a vector field

Kuruman is right..the distribution is not uniform, it depends from r...look at the thread i posted few days before by the title ''Gauss Law'' by Engels and u will find the solution. I had almost the same problem as you and i solved it

I will give u all the equations u need(i think) and try to solve it by urself I=dQ/dt dQ=nqvAdt thus I=nqvA n is the charge concentration, v the electrons velocity, A surface area J=I/A J is the current's density v=J/nq hope i helped

when i find the time i will post the entire problem with the solution so others can see... this was my first experience in this site and i found it very useful and nice :) excellent...and u guys rulez..

Ok boys i solved..i took ,like before, those two ,indefinite now, integrals and solved them to find E my mistake was that before i took those two definite integrals from 0 to R

i said dA=8πrdr and dV=4πr^2dr and r from 0 to R and did the maths..u can try it but u can't result to the desire equation...i took E as constant in the integral and solved by E can u think of anything different ?

Thanx for the reply but it doesn't help to much.. The charge distribution is not uniform inside the volume and it behaves according to this equation ρ=ρ0(1-r/R) p= charge density R=radius of the main volume and r= radius of the gauss surface.. and ρ0=3Q/πR^3 and it is constant I need to...

i tried the following path without success \int E dA=Qenc/ε0 but Qenc=\int p Dv therefore \int E dA equals \int p Dv i figure out how dV is so change it with the equal dr expression so i did for dA..i idi the math math but no result equal the solution i wrote above... any help is...

Homework Statement One ,non uniform but spherical in symmetry distribution of charge has charge density which is given by the following equations ρ=ρο(1-r/R) when r< R and ρ=0 when r>R, ρ0=3Q/πr^3 and it is constant a) show that the total charge included by this distribution is equal to Q...