Pendulum the pendulum could be used to measure the force of gravity. During his expedition to Cayenne, French Guiana in 1671, Jean Richer found that a pendulum clock was minutes per day slower at Cayenne than at Paris. From this he deduced that the force of gravity was lower at Cayenne. In 1687, Isaac Newton in "Principia Mathematica" showed that this was because the Earth was not a true sphere but slightly oblate (flattened at the poles) from the effect of centrifugal force due to its rotation, causing gravity to increase with latitude. Portable pendulums began to be taken on voyages
Kapitza's pendulum become stable in Kapitza's pendulum. The rotating solutions of the Kapitza's pendulum occur when the pendulum rotates around the pivot point at the same frequency that the pivot point is driven. There are two rotating solutions, one for a rotation in each direction. We shift to the rotating reference frame using formula_59 and the equation for formula_39 becomes: Again considering the limit in which formula_5 is much higher than the proper frequency formula_38, we find that the rapid-formula_5 slow-formula_65 limit leads to the equation: The effective potential is just that of a simple pendulum equation. There is a stable equilibrium