- 12π√ℓg\frac{1}{{2\pi }}\sqrt {\frac{\ell }{g}}
- 2π√gℓ2\pi \sqrt {\frac{g}{\ell }}
- √ℓg\sqrt {\frac{\ell }{g}}
- √gℓ\sqrt {\frac{g}{\ell }}