# How do I find the velocity that an electron must acquire

1. Dec 6, 2004

### irony of truth

How do I find the velocity that an electron must acquire, if its mass is to be equal to the rest mass of a proton?

I know that the masses of electron and proton are 9.11 X 10^-31 kg and 1.67 X 10^-27 kg, respectively.

Am I going to use the formula m = m_0 / (1 - v^2/c^2)^(1/2) ?

How do I continue from here?

2. Dec 6, 2004

### dextercioby

Let's approximate this number,okay??
$$\frac{9.11\cdot 10^{-31}}{1.67\cdot 10^{-27}}\sim \frac{1}{1836}$$

I'll give u the final answer and let u work out your way through to it.
$$v=\frac{\sqrt{1836^{2}-1}}{1836} c$$

Good luck!!

3. Dec 6, 2004

### irony of truth

Hmm, I just got your reply.. seems like it is almost the same as the speed of light... amazing!

4. Dec 6, 2004

### dextercioby

Judging it in the context of SR,it's not surprising,let alone amazing.So,by "I just got your reply" does it mean you solved the problem and confronted the result with mine ??Hopefully so,it would mean that the PF community did its job and got u happy and satisfied...

5. Dec 7, 2004

### irony of truth

Hi! What I mean is that when I saw your hints, I quickly solve the problem - knowing that my first idea is correct... but I did not confront your answer... I just saw that I got the correct solution.. same as yours.

But I thank you for helping me.