Register to reply

Length of the vector (electrostatic cylinder)

by Blastrix91
Tags: cylinder, electrostatic, length, vector
Share this thread:
Nov19-12, 10:04 AM
P: 25

My problem is that I'm confused about a hint I was given in this problem. I usually use the law of cosine to find the length of [itex]\vec{r}-\vec{r'}[/itex]. But the hint here says that I should make it [itex][r^2 + (z - z_0)^2]^{1/2}[/itex]

Where does this come from? I can't quite get my head around the geometrical idea of this hint. Can't the law of cosine be used here?
Phys.Org News Partner Physics news on
Symphony of nanoplasmonic and optical resonators produces laser-like light emission
Do we live in a 2-D hologram? New Fermilab experiment will test the nature of the universe
Duality principle is 'safe and sound': Researchers clear up apparent violation of wave-particle duality
Nov19-12, 10:16 AM
P: 1,212
It's really hard to answer these questions when you don't specify what any of the terms mean, so I can only guess at what r-r' even is. It looks like a Pythagoras approach to give you the hypotenuse of the triangle with sides r and z-z0.

How would you use the law of cosine, and what problem would using it solve?
Nov19-12, 01:26 PM
P: 1,969
I don't know how the hint is specifically formulated but I think the best way here is to use cylindrical coordinates.
It may be that r' is the cylindrical radius of the charge element.
The point P has r=0 and z=zo.

Register to reply

Related Discussions
Moment of inertia of hollow cylinder, axis orthogonal to length Classical Physics 4
Gauss's law, cylinder of length L Introductory Physics Homework 6
Casimir effect and a finite length Tipler cylinder? General Physics 0
Solve for the length of a cylinder Introductory Physics Homework 2