Free-Fall Pendulum

## Question:

Mr. Jones

I was curious as to what would happen to a pendulum that was in free-fall (apparent weightlessness). Someone mentioned that it would rotate around its axis. If this is true, could you please explain. Thank you

## Answer:

Hi Tom,

Let's imagine that we have a pendulum attached to a pivot point fixed in the space shuttle in Earth orbit. If the pendulum was given an initial push, it would rotate about the pivot point until air resistance and friction used up the initial energy. If the pendulum was initially released with zero angular velocity relative to the shuttle, assuming very low pivot friction, any reorientation of the shuttle in the plane in which the pendulum is free to swing will result in apparent repositioning of the pendulum. For example, if the shuttle with its long axis parallel to the orbit track maintains a bay-down attitude relative to Earth, a pendulum aligned to swing freely parallel to the long axis of the shuttle will complete one revolution each orbit.

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JDJ