# Number say about the spin of a particle?

1. Jun 8, 2009

### MrPickle

What does the number say about the spin of a particle?

Like for an quarks it's half, what does it mean by 1/2 spin?

2. Jun 8, 2009

### malawi_glenn

Last edited by a moderator: May 4, 2017
3. Jun 8, 2009

### clem

Re: Spin

The number like 1/2 is the magnitude of the maximum z component of the spin angular momentum in units of hbar. That is, (1/2)hbar would this magnitude in whatever units you use for hbar.

4. Jun 8, 2009

### Staff: Mentor

Re: Spin

It means that the particle has an intrinsic angular momentum with magnitude

$$|\vec S| = \sqrt {s(s+1)} \hbar =\sqrt{\frac{1}{2} \left(\frac{1}{2} + 1 \right)} \hbar$$

which works out to $9.14 \times 10^{-35}$ kg-m2/sec.