Oscillations ** 3A60.40 ** Driven mechanical resonance

Driven mass on a spring

Equipment:

• dragon on spring, on stand - in front of shelf 10
• Daedalon precision sine drive - in front of shelf 10
• Synchron stepper motor - in front of shelf 10

Theory: When a system like a toy dragon on a spring is driven at its natural frequency of oscillation, resonance occurs. Even though the motion of the driver has an amplitude of only a couple of cm, the amplitude of the dragon's oscillation can be as much as 30 cm.

Description: This resonant system is set up and ready to go. There is both a coarse and a fine frequency control on the driver, with the position at resonance marked. If you start off-resonance, building up a low amplitude oscillation (with beats), and then move to resonance, be patient; it takes two or three minutes for the amplitude to build up. When tuned correctly, the dragon will almost reach the base of its support stand.

Setup time: 3 minutes.

References: (available in the demo room)

• Sutton, "Demonstration Experiments in Physics", S-13, p. 132.
• Ehrlich, "Turning the World Inside Out", G.5, p. 93.