# [ Spring pendulum ] Centrifugal Force transmissibility

1. Dec 5, 2011

### nzur

Hey folks,

Assume that there is a spring pendulum rotating at hinge (Free swing or forced swing).

In this case, can I calculate force transmissibility (transmitted force amplitude to ground via spring devided by centrifugal force amplitude) ?

or is it not logical because centrifugal force is not excitation force to the system ?

The point is, if there is a rotation, spring would vibrate more than the case w/o rotation. So I want to quantify how much the rotation affect to the vibration.

Does it make sense to you?

Any kind of comment will be very appreciated. Thanks!

2. Dec 18, 2011

### Simon Bridge

If you construct a pendulum so the usual string is replaced by a spring, you get what is more usually the case - a real pendulum string is a bit stretchy. The restoring force from the spring provides the tension keeping it on a curved path.

The other image that comes to mind is a rotor made from a mass on the end of a spring.

To both systems you could add oscillations.

If you wanted to know how the normal mass-on-a-spring oscillations are affected by being in a rotating system - then it would make sense to use centrifugal force (eg. if you did the mass-on-a-spring experiment inside a rotating space-station).