Physics 111 Lab: The Physical Pendulum
In this lab, you will measure several different frequencies of oscillation of a physical pendulum. From this data, you will get a relatively precise value of g. So, the goal here is to measure g using a physical pendulum.
The physical pendulum you will be investigating is a meter stick.
Here’s what you will do:
1. Starting with the formula for the frequency of the physical pendulum and the parallel axis theorem, derive a formula for g in terms of the period of oscillation of the physical pendulum T, the distance from the pivot point to the center of mass of the ruler d, the length of the ruler L, and fundamental constants. This will go in the Theory section of your report. (Remember to define your variables.)
2. Determine the period of oscillation for at least 5 different d’s. It is up to you to determine the best way to get your ruler to oscillate. You may want to put small holes in the ruler. That would be OK, but if you are doing that, pick an old, crummy-looking ruler. Of course, it is best to time how long it takes to go back and forth several times and divide this by the number of times it went back and forth to get the period.
3. You now have five values of d, each with a corresponding value of T. Use these and the formula you derived above to come up with five different values of g.
4. Average your five values of g. This is the value you report.
5. Find the standard deviation in the five values of g. This is your uncertainty in your measurement of g.
6. Write your usual report. This one is easy to write as you do things.
Name/Partners/Date/Title
Introduction – State the purpose of the experiment.
Theory – Put your derivation of your formula for g here.
Experiment – Describe how you set up your oscillating meter stick and how you measured d and T. Include equipment numbers and enough details that someone years from now could exactly duplicate what you did.
Analysis – Crunch your numbers. Determine your average and standard deviation in g here.
Discussion – Compare your measured value of g to 9.8 m/s2. Do they agree? Why or why not? If your result is not reasonable, go back and check your work, and retake data if necessary! Don’t turn in flawed results.
Conclusion – Restate your value for g and its uncertainty. Sum up why you think this is reasonable. Nothing new should go here.