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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 . Lab 11 Mechanical & Acoustical
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Physics 145 Introduction to Experimental Physics I Instructor: KarineChesnel 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
Lab 11 Mechanical & Acoustical Resonators
Mechanical resonators Spring – mass resonator Pendulum
At rest • In motion - kx - bv mg Fexternal Mechanical resonators Second Newton’s law
Analogy with RLC circuit • Complex notation Mechanical resonators - kx - bv mg F0
Velocity detector Oscillation visual meter oscillator Driving Force device Damping element Mechanical resonators
Read Amplitude Peak to peak Mechanical resonators
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 App vs. f • L10.4: Fit the data to resonance peak (in Mathematica) • - deduct a refined value for k and for b
Acoustical resonators Music instruments
Acoustical resonators Helmholtz resonator
Acoustical resonators Helmholtz resonator See derivation at http://www.phys.unsw.edu.au/jw/Helmholtz.html
Acoustical resonators Helmholtz resonator experiment
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)