A pendulum that was originally erected by Foucault at the Pantheon in Paris for the Paris Exhibition in 1851 was restored in 1995.It has a 28.0-kg sphere suspended from a 67.0-m light cable.How long would it take for the bob in this pendulum to move from the position of maximum displacement down to the equilibrium point?
A)4.11 s
B)21.5 s
C)2.58 s
D)32.2 s
E)42.9 s

Question

Quizplus · Accepted Answer

The period of a pendulum is given by:$$T = 2\pi \sqrt{\frac{L}{g}}$$where L is the length of the pendulum and g is the acceleration due to gravity.In this case, L = 67.0 m and g = 9.81 m/s^2.So, the period of the pendulum is:$$T = 2\pi \sqrt{\frac{67.0 	ext{ m}}{9.81 	ext{ m/s}^2}} = 16.4 	ext{ s}$$The time it takes for the bob to move from the position of maximum displacement down to the equilibrium point is half of the period, or:$$t = \frac{T}{2} = \frac{16.4 	ext{ s}}{2} = 8.22 	ext{ s}$$So, the correct answer is A) 4.11 s.

A Pendulum That Was Originally Erected by Foucault at the Pantheon