Joey KingGavin Wagner

Joe TomasAllison CarlosAnne Ethridge

Pendulums

• The formula for the period of a pendulum is:

• Where L= length of string and g=9.80m/s^2

PERIOD OF A PENDULUM

FBD for a Simple Pendulum• Tension in a simple pendulum cannot cancel with the

force due to gravity.• There cannot be any motion in the direction of

tension so that the string keeps its length• The force perpendicular to tension is mgsinӨ• *if Ө is small, sinӨ=Ө, but only in radians

• Since we know that a pendulum is in simple harmonic motion, we can derive the formula for the period using Hooke’s Law F=-kx:

• X=LӨ and k=mg/L• So:• T=2π√(L/g) where L=gt^2/4π^2

WHY?

1. What is the frequency of a pendulum with a length of 60.96 cm?2. What is the length of a pendulum with a period of 10 seconds?3. Suppose you are an astronaut and need to find the acceleration due to gravity on an asteroid using a pendulum. The period of the pendulum is 20 seconds and the length of the pendulum is 10 cm. What is g?

EXAMPLES!

1. f = 1/T = 1/1.57 s = 0.647 Hz2. L=24.8 m 3. g=0.01 m/s^2

Answers!

• https://www.youtube.com/watch?v=yVkdfJ9PkRQ