If the period of a simple pendulum is to be 3.91 s, what should be its length?

The period of a simple pendulum is given by the formula:

T = 2π√(L/g)

where T is the period, L is the length of the pendulum, and g is the acceleration due to gravity.

Rearranging the formula to solve for L:

L = (T/2π)² * g

Substituting the given values:

L = (3.91 s / (2π))² * 9.8 m/s²

Calculating the length:

L ≈ (0.621 s)² * 9.8 m/s²

L ≈ 2.446 m

Therefore, the length of the simple pendulum should be approximately 2.446 meters.