# How do i convert ?

#### gunblaze

I was reading a book on the theory of relativity yesterday and it said that by substituting the equation for momentum (p=mv) in to the formula E^2=m^2c^4+p^2c^2..
i will be able to get this E=gamma mc^2..
I was just wondering where they get the "gamma" from? can anyone pls tell me how they get that? Thx
sry, not really good at this.

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#### Pengwuino

Gold Member
gamme is equal to 1 over the square root of 1-((v^2)/(c^2))

#### dextercioby

Homework Helper
You need to be careful with the notation.

$$E^{2}=m^{2}c^{4}+p^{2}c^{2}$$

and $$p=\gamma m v$$.

Daniel.

#### gunblaze

dextercioby said:
$$p=\gamma m v$$.
Isn't momentum=mass x velocity?

#### Pengwuino

Gold Member
gunblaze said:
But isn't momentum=mass x velocity?
Not in relativistic physics. Its gamma * mass * velocity as v -> c

#### gunblaze

erm.. can we put velocity, v, and speed of light, c, together?
eg: $$v^{2}c^{2}=c^{4}$$

Last edited:

#### gunblaze

but it sounds ridiculous rite? how can the velocity be equal to the speed of light?

#### gunblaze

k.. guys, i get it alr..thx thx so much!

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