# Angular Displacement in Rotational Dynamics

1. Nov 6, 2005

### cscott

Why do we use the angle as the base quantity in rotational dynamics instead of, perhaps, arc length? Is it because angular displacement is easier to measure? Would it make any sense to use arc length?

2. Nov 6, 2005

### ZapperZ

Staff Emeritus
Arc length depends on the radius that you choose, so you always have to indicate the radius you are using that corresponds to that arc length. Angular displacement doesn't.

Zz.

3. Nov 6, 2005

### cscott

Oh, that makes sense. Thanks!