Orbital and spin angular momentum

1. Jul 27, 2008

spidey

what are the formulas for orbital and spin angular momentum? Or both have the same formula?

The formula J=mvr is for orbital or spin angular momentum?

2. Jul 27, 2008

vkroom

spin is not a derivable quantity in the sense if orbital angular momentum. So you can't have such a classical expression for it.

J=mvr is the orbital angular momentum, albeit in a the classical sense.

quantum mechanically one can't have such formulae. Its a bit different in this regime.

3. Jul 27, 2008

spidey

if J=mvr is the orbital angular momentum then how to calculate spin angular momentum..

for example,earth spins on its own axis so how to calculate earth's spin angular momentum...some black holes also spin so how to calculate?

4. Jul 27, 2008

vkroom

dude, u shud be clear as to what you mean by spin.

if its the usual spin in physics, i.e. the one ppl talk abt in particles like electrons, then its not what u are writing here.
if its earth's spinning rate u wanna know, then its still the same old angular momentum, bt for something known as a "rigid body" rotation. its given as : L = Iw. wiki a bit and u'll be through.

angular momentum and spin for quantum object are not defined by such formula as mentioned above.