Coupled Series Masses Hanging On Springs

Purpose

To illustrate coupled oscillations and normal modes.

Equipment

Two identical rubber corks hanging from two identical small springs as photographed.

Images

g2-27

Description

Pushing either mass causes oscillations which will couple between the two masses. If the two masses are displaced from equilibrium by the appropriate amount either (1) in phase, or (2) out of phase, the normal modes can be produced. Alternatively, moving your hand up and down at the frequency of a normal mode will excite that mode.

References

William Pong, Principal Frequencies of a Double Spring-Mass System, AJP 21, 546-548, (1953).