# Electrons - Relativistic velocity addition

1. Aug 6, 2012

### charmedbeauty

1. The problem statement, all variables and given/known data

an observer measures the velocity of two electrons, finding one with a speed c/2 in the x direction and the other c/2 in the y direction. what is the relative speed of the two electrons.

2. Relevant equations

3. The attempt at a solution

Im not sure if this is right it seemed to easy.

but suppose that electron 1 is called b and the other a

then v(b)= √(c2/4+c2/4)
since they are at right angles to each other. is this right?

2. Aug 6, 2012

### voko

Re: electrons

The velocities are very high, you need to use special relativity here.

3. Aug 6, 2012

### phinds

Re: electrons

No. That is a non-relativistic velocity-addition and would give you the right answer for a speeding bullet on Earth but NOT for things traveling at relativistic speeds.

4. Aug 6, 2012

### charmedbeauty

Re: electrons

oh yeah that makes sense ok cool thanks.

5. Aug 7, 2012

### KingBigness

Re: electrons -- Relativistic velocity addition...

How did you go with the rest of the assignment =P