1. Physics 145 Introduction to Experimental Physics I Instructor: Karine Chesnel Office: N319 ESC Tel: 801- 422-5687 kchesnel@byu.edu Office hours: on appointment Class website: http://www.physics.byu.edu/faculty/chesnel/physics145.aspx

3. Lab 11 Mechanical & Acoustical Resonators

4. Mechanical resonators Pendulum Spring – mass resonator

5. Mechanical resonators F external mg - kx - bv In motion Second Newton’s law At rest

6. Mechanical resonators F0F0 mg - kx - bv Analogy with RLC circuit Complex notation

7. Mechanical resonators Damping element Driving Force device Oscillation visual meter Velocity detector oscillator

8. Mechanical resonators Read Amplitude Peak to peak

9. Lab 11: Resonators A. Damped Mass-Spring Oscillator L10.1: Set up apparatus L10.2: Predict the resonance frequency of oscillator (measure m, k, and b) Simulate the frequency response L10.3: Measure the frequency response of the oscillator - measure the peak-to-peak amplitude at each point (wait for stabilization for each point in frequency) - plot your data A pp vs. f L10.4: Fit the data to resonance peak (in Mathematica) - deduct a refined value for k and for b

10. Acoustical resonators Music instruments

11. Acoustical resonators Helmholtz resonator

12. Acoustical resonators Helmholtz resonator http://www.phys.unsw.edu.au/jw/Helmholtz.htmlSee derivation at

13. Acoustical resonators Helmholtz resonator experiment

14. Lab 11: Resonators B. Helmholtz Resonator L10.5: Play with the resonator (blow into it) L10.6: Set the experiment up - Locate the resonance frequency - optimize the position of the speaker L10.7: Measure the frequency response of the resonator with a microphone (plug into computer jack) Create a Labview program to read the signal and sample at 20kHz, over 0.1s L10.8: Map out the frequency response L10.9: Measure the resonance frequency and compare with prediction (measure A, V and l)