Driven Mass on a Spring

A spring with a mass attached is hung by a string that is wrapped over a pulley and connected to an armature rotated by a variable-speed motor. Operation of the motor will drive the spring-mass system and cause it to oscillate. If the motor is run at the mass-spring system's resonance frequency, the amplitude of the motion becomes so great that the string jumps off of the pulley.

M1, F3

Setup

To set up:

  1. mount pulley on a rod clamped at the corner of the table, diagonally away from the table (this ensures that the mass won't hit the table at resonance)
  2. attach one end of the string with a loose knot to the knob on the disk attached to the motor (not too tight! or the string will be winded around the knob)
  3. pass string through pulley and hang tapered spring from it (narrow side up); there are different springs with different constants
  4. at the free end hang a 100 - 1000 g mass, usually a 200-500 g mass works best with most springs
  5. turn on motor and adjust speed until resonance is achieved (to turn on, make sure top knob is in a non-zero position and turn bottom left knob to forward or reverse, does not matter)
  6. if there is no string, find more string in drawers next to 120

PIRA DCS 3A60.40