# Homework Help: Special Relativity of electrons

1. Jun 1, 2009

### whitehorsey

1. How close would two stationary electrons have to be positioned so that their total mass is twice what it is when the electrons are very far apart?

2. p = (mv) / (squareroot(1-(v2/c2))
E = (mc2) / (squareroot(1-(v2/c2))
E = mc2
m = (rest mass) / (squareroot(1-(v2/c2))
L = (proper length)*(squareroot(1-(v2/c2))

3. m = 2(rest mass)
m = (rest mass) / (squareroot(1-(v2/c2))
v = 6.75 * 1016

I solved up to the velocity but I don't know how to calculate the distance.

1. A spacecraft approaching the earth launches an exploration vehicle. After the launch, an observer on earth sees the spacecraft approaching at a speed of 0.50c and the exploration vehicle approaching at a speed of 0.70c. What is the speed of the exploration vehicle relative to the spaceship?

2. u = (u' + v) / (1 + (u;v/ c2))
u' = (u - v) / ( 1- (uv/c2))

3. I attempted this problem by setting u' equal to each other (each u either represents the exploration vehicle or the spaceship). But, I got stuck. I didn't know which v was for which vehicle/spaceship.

2. Jun 1, 2009

### Andrew Mason

The electrical potential energy has to equal 2me2. What is the expression for that potential energy in terms of distance between the electrons?

Use http://hyperphysics.phy-astr.gsu.edu/hbase/relativ/einvel.html#c1"

AM

Last edited by a moderator: Apr 24, 2017