Foucault pendulum sharing the rotation of the earth about its own axis, the suspension point of the pendulum traces out a circular path during one sidereal day. At the latitude of Paris, 48 degrees 51 minutes north, a full precession cycle takes just under 32 hours, so after one sidereal day, when the Earth is back in the same orientation as one sidereal day before, the oscillation plane has turned by just over 270 degrees. If the plane of swing was north-south at the outset, it is east-west one sidereal day later. This also implies that there has been exchange of momentum;
Foucault pendulum vector diagrams be determined. The inverse ratio will determine the time observed for one full rotation of the pendulum swing in comparison to the duration at the pole of one day. From the diagrams two points of the pendulum swing can be chosen to project straight down to two points on opposite sides of the Earth (180° apart). This makes it easy to obtain the velocity vector difference and then the time observed for a full rotation from the inverse ratio. The examples show that the Earth turns underneath the plane of the pendulum swing and how this change in relationship can