Physics 145 Introduction to Experimental Physics I Instructor: Karine Chesnel Office: N319 ESC Tel: Office hours: on appointment Class website:

Lab 11 Mechanical & Acoustical Resonators

Mechanical resonators Pendulum Spring – mass resonator

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

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

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

Mechanical resonators Read Amplitude Peak to peak

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

Acoustical resonators Music instruments

Acoustical resonators Helmholtz resonator

Acoustical resonators Helmholtz resonator derivation at

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)