# A Pendulm's circular motion.

1. Jan 22, 2006

### abar45

My teacher for Physics hns proposed an extra credit bonus if any one could answer this question dealing with a pendulm. Why does the pendulm move as if it had a mind of its own. Refering to the circular motion the pendulm starts making after a couple seconds. When the pendulm is released to go in a back and forth motion (a straight line) it starts off straight but then starts to make a circular motion, usually counter clockwise. What is the reason in lamens terms for it's circular path. Please!

2. Jan 22, 2006

### pseudovector

I think it's caused by Coriolis force. Take a merry-go-roung for example, revolving at a constant angular velocity. Different part, at different distances from the rotation axis will move at different velocities, so if something moves away or towards the axis, it will feel the speed change, it will experience acceleration. The cause of that acceleration is the Coriolis force.
Since the earth revolves around itself, then anything that moves towards or away from the earth will experience the Coriolis force.