Measuring E & B Fields in Moving Frame

[whatsapro]

Homework Statement

Suppose E and B are measured by an ovserver at rest to be (in N/C)
E = [0,0,60] B = [0,0,0]

Now another observer travels close by in the +x direction at a constant speed of v = .8c with respect to the other observer.

A. What is E' be in the moving frame? DONE
b. what will B' be in the moving frame? DONE
c. If a charge q = 1micro C travels with the moving observer (v = .8c in the +x direction), what is the direction of F(em) according to the observer at rest?

d. what is the direction of F(em) according ot the observer moving along witht he charge?

Homework Equations

I assume F(em) = q[E + v/c X B] or the other ref frame version

The Attempt at a Solution

Which one do I use? If the observer is at rest, wouldn't he be seeing the v = .8 c ? That would not even matter cause B = 0 anyways right? I would still use F(em) = q[E + v/c X B] right?

for part D. I would use F'(em) = q[E' + v'/c X B'] where v' = ? would it be 0 because they are traveling same v?

I understand that F(em) ne F'(em) but what is also confusing is that in both cases, the E field is the only contributing factor to the force. Is that assumption true?

 

[whatsapro]

Am I missing something here? Its copied exactly how it is written on paper.