Re: OT- Relativistic mechanics and such - was - Re: tbird problem

[John Hasler <john@sugarbit.com>]

Van Snyder writes:
>Radation has mass, as can be seen from m = E/c^2.

Radiation has momentum but no mass.  The correct full equation is

E^2 = (p^2)*(c^2) + (m^2)*(c^4)

where E is energy, p is momentum, c is the speed of light in a vacuum,
and m is rest mass.

For massive particles moving at low speeds the first term is negligible
and so the equation simplifies to E = m*c^2.  For massless particles
(which always move at c in all reference frames) it simplifies to
E = pc.  Photon momentum is p = h/λ where h is Planck's constant and λ
is wavelength.

https://en.wikipedia.org/wiki/Momentum#Relativistic

-- 
John Hasler 
john@sugarbit.com
Elmwood, WI USA