# Homework Help: Speed of particle Galilean relativity

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1. Jun 10, 2015

### j3dwards

1. The problem statement, all variables and given/known data
Two particles are created in a high-energy particle accelerator and move off in opposite directions. The speed of one particle, as measured in the laboratory, is 0.650 c, and the speed of each particle relative to the other is 0.950 c, where c = 3 × 108 m/s is the speed of light in vacuum.

What is the speed of the second particle, as measured in the laboratory? Compare your result to what you would obtain from Galilean relativity.

2. Relevant equations

u' = u - v

3. The attempt at a solution
So galilean relativity says that the laws of motion are the same in all intertial frames.

So the speed of the second particle is just: 0.950 c - 0.650 c = 0.300 c

correct?

Last edited: Jun 10, 2015
2. Jun 10, 2015

### Staff: Mentor

Earlier you wrote:
So there's a typo somewhere.

But that's the right idea for Galilean relativity. What about special relativity?

3. Jun 10, 2015

### j3dwards

Oh yes sorry, so the speed of the second particle is 0.300c.

And for special relativity: u' = u - v/(1-uv/c2) = (0.950c - 0.650c)/(1-(0.95c x 0.650c)/(c2) = 2.35 x 108 = 0.784c

Is this right?

4. Jun 10, 2015

### Staff: Mentor

Looks good to me!