J·s
joule second
Angular momentumexact by definition
The joule second is exactly equal to the kilogram square metre per second, since a joule is kg·m²/s². The two are the same unit under different names, and the equality is exact. Quantum mechanics prefers this form because the Planck constant, whose fixed value is 6.62607015 × 10⁻³⁴ J·s, is itself an angular momentum.
Watch out: The reduced Planck constant \(\hbar = h/2\pi\) is the natural quantum of angular momentum, and particle spins are quoted as multiples of it. A spin-1/2 particle has angular momentum \(\hbar/2\), about 5.27 × 10⁻³⁵ J·s. Do not mix \(h\) and \(\hbar\), which differ by a factor of \(2\pi\).
| 1 J·s | 1 kg·m²/s |
Solvers that use angular momentum