there is a sraight wire carrying current i. an electron is approaching the wire, in the same plane as the wire, at a 45 degree angle with velocity v0 when it is a distance r0 from the wire. the electron makes it to a distance of rf from the wire before it is repelled away. what is i? I was thinking that I know that K.E.=Me(v0*sin(45))/2 initially in the y direction (this would be the y-component of K) if y is taken as the coordinate perpendicular to the wire and x the one parallel to the wire. K.E.=0 once the electron is at a distance of rf. I also know that Work=integral Fdr in the y direction. so here is an equation that should work: K.E.=Me*v0*sin(45)/2=[inte][e*vx*mu0*i/(2*pi*r)]dr from r=r0 to r=rf e=charge of electron mu0=permeability of free space vx=x-component of velocity i=current i'm trying to solve for r=dist. from wire the problem is that i can't figure out a way to express vx as a function of r so that i can integrate this. somebody help!! thanks, rick.