# Question #e7a66

Feb 27, 2017

The length is $= 1 m$

#### Explanation:

The period of a simple pendulum is

$T = 2 \pi \sqrt{\frac{L}{g}}$

Period $= T s$

Length $= L \left(m\right)$

Therefore,

$\frac{L}{g} = \frac{T}{4 {\pi}^{2}}$

In the first case, we have

$L = \frac{T g}{4 {\pi}^{2}} = \frac{{4}^{2} \cdot 9.8}{4 {\pi}^{2}} = 4 m$

In the second case,

$T = \frac{60}{30} = 2 s$

So,

$L = \frac{4 \cdot 9.8}{4 {\pi}^{2}} = 1 m$