Hey, just need a physicist to clarify something for me. I'm trying to work out the energy of a projectile travelling at a significant fraction of c. i only know the rest mass and the velocity.

 

as far as i can make out, the equation to use is:

 

Ek= mc²(1/sqrt(1-v²/c² - 1)

 

i'm not sure whether the m is relativistic mass or rest mass. if it's rest mass then all is good, if it is relativistic mass then can someone show me the proper equation?

It's the rest-mass. Your equation lacks a ")" which supposedly is a typo. [math]E_{\text{kin}} = E - E_0 = m_{\gamma}c^2 - m_0c^2 = \gamma m_0 c^2 - m_0 c^2 = (\gamma - 1) m_0 c^2[/math] where [math]m_{\gamma}[/math] and [math]m_0[/math] are relativistic mass and rest-mass, respectively.

Your equation lacks a ")" which supposedly is a typo.

 

Thats the typo that usually causes my source code to fail to compile

 

thanks for the help.