Question

The period of a pendulum is the time the pendulum takes to swing back and forth one full-time. The function l = .81 t^2 relates the length l in feet of a pendulum to the time t in seconds that it takes to swing back and forth. The convention center in Portland, Oregon, has the longest pendulum in the U.S. The pendulum's length is 90 ft. Find the period for this pendulum.

a. 8.5 seconds
b. 10.5 seconds
c. 90 seconds
d. 111 seconds​

Answer 1

The given formula is L = 0.81t^2

L is given as 90 ft.

Solve for t:

90 = 0.81t^2

Divide both sides by 0.81

t^2 = 90/0.81

t^2 = 111.11

Take the square root of both sides:

t = √111.11 = 10.54 = 10.5 seconds.

The answer is b.