Teaching Physics with the Physics Suite

Edward F. Redish

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The PhET simulation team have a simulation that shows a mass on a spring being driven by an oscillating base as shown in the figure at the right. You can access this simulation at http://phet.colorado.edu/en/simulation/resonance.

A. Set the parameters of the oscillator as follows:

• One resonator
• Mass of resonator, m = 1.0 kg
• Spring constant, k = 25 N/m
• Damping constant, b = 0.1 N-s/m.

On the palette where you set the oscillator parameters it quotes "frequency = 0.796 Hz." Is this the natural frequency (in cycles/sec = Hz) of the undamped oscillator (with b = 0) or for the damped oscillator? Explain the difference and how you calculated them.

B. When you set the driving frequency to be well below this (say f = 0.6 Hz) does the mass oscillate with (in phase) with the driver or opposite to it (out of phase)? What happens when you the the driving frequency above the natural frequency (say f = 1.0 Hz). In phase or out of phase?