Experiment The Damping Effect Of Air Drag On A

experiment: the damping effect of air drag on a pendulum bruce dillon lane matheson carol brunjes objective: to show students the

Experiment: The Damping Effect of Air Drag on a Pendulum
Bruce Dillon
Lane Matheson
Carol Brunjes
Objective: To show students the damping effects that occurs due to air
drag and heat loss.
Materials:
*
Simple Pendulum
*
Stop watch
*
Ring Stand
*
Graph paper
*
Cardboard protractor large enough to measure angles at the bottom
of the pendulum
*
Tape
Procedures:
1.
Set up pendulum and protractor as shown.

2.
Measure the length of the top of the string to the center of the
mass. Record in data table.
3.
Pull the mass back to an angle of approximately 40 degrees.
Record angle in data table.
4.
Release the mass and measure the maximum angle every 15 seconds.
Continue until angle is 5 degrees or less. Record angles in data
table.
Discussion:
A simple pendulum produces simple harmonic motion when the
displacement from the equilibrium position is small. The small angle
is used to reduce the amount of drag due to the air. However, if the
angle is large then drag needs to be considered. In this case the
oscillations of the mass of the pendulum are subject to a drag force
proportional to the velocity. The system is the said to be “damped”.
In damped oscillations the amplitude decreases exponentially with
time.
Questions for Students:
1.
Graph your data with amplitude on the y-axis and time on the
x-axis.
2.
Does your data agree with theory? Explain your response.
3.
At what value of t would you expect your pendulum to stop
completely?
4.
What are some errors that might skew your data?
5.
As amplitude decreases, what happens to the periods?