Classes of “collapse and oscillation” that result from removing support from a loop in different ways. The black (solid) line shows the loop position as a function of time and the red (dashed) line shows the equilibrium position, which is moved to drive the system. a) Impulsively excited loop oscillations result if support is removed rapidly compared to the oscillation period. b) Gradual displacement is produced if support is removed slowly compared to the oscillation period. c) Oscillation during collapse is seen if support is removed on a time scale broadly similar to the oscillation period.