Measurement of a spring force constant using sound, door alarm, and soundcard oscilloscope

Abstract

The increasing or decreasing magnetic field of a permanent magnet—attached to the bottom of the mass hanger of a spring-mass oscillator—would turn ON or OFF, respectively, the switch of a door alarm system. The sound pulses—now voltage pulses as a result of conversion by the built-in microphone of a PC—were recorded by the PC-based oscilloscope as a function of time and on the basis of these data, the period of oscillations was obtained; thus, the spring constant. We obtained (29.6 ± 0.1) N m−1 which is a good match to the accepted value of 30.0 N m−1.