PASCO Essential Physics Teacher Lab Manual Instructions
- June 9, 2024
- PASCO
Table of Contents
Investigation 14C: Resonance
Essential Physics Teacher Lab Manual
Essential Question: What is resonance?
When periodic forces are applied to a system that can oscillate, the
resulting motion can vary tremendously. If the frequency of the force matches
a natural frequency of the system, a very large amplitude response can occur.
The extra-large response is what we call resonance.
Part 1: Finding the natural frequency
- Attach the pendulum clamp to the top of the rod.
- Hang the loose long spring from the pendulum clamp screw closest to the rod. Hang the brass pendulum from the spring.
- Pull the mass down slightly to start it oscillating.
- Measure the time for ten oscillations.
Questions
a. What is meant by the oscillator’s “natural frequency”?
b. What are the values of your oscillator’s natural period and frequency?
Table 1: Measured frequency and period
| Trials
---|---
| I| 2| 3| 4| 5| average
frequency| | | | | |
period| | | | | |
c. Describe and then apply a method to estimate the error bars on your
frequency measurement.
d. Describe the meaning of the terms phase and amplitude.
Part 2: Creating resonance
- Remove the spring from the pendulum clamp and hold it with your hand.
- Use the timer to beep at a set time interval.
- Each time the timer beeps, give the spring a small upward jerk.
- Have your partner estimate the amplitude of the motion using a meter stick after 4-5 beeps.
- Measure and tabulate the oscillation amplitude for at least ten frequencies between 1/4 and 3x the natural frequency. Try frequencies that are 3x, 2.5x, 2x, 1.5x, 1x and fractions of the natural frequency measured in Part 1. Convert the desired frequency to period to enter the value in the timer.
- Graph the oscillation amplitude versus the frequency of the periodic force.
Questions
a. In your own words, define resonance by referring to the motion you just
observed and the graph of your data.
b. At what frequencies is the oscillator in resonance? At what frequencies is
it out of resonance?
c. Describe the flow and storage of energy in the system at resonance compared
to frequencies that are not at resonance.
d. Prepare a written report for your investigation (parts 1 and 2). In
addition to addressing the above questions, describe the procedure, results,
and conclusion (or interpretation) of your investigation
Table 2: Amplitude as a function of frequency
| Frequency (Hz) | Period (s) | Amplitude (cm) |
|---|---|---|
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