If a physical pendulum has the same period of oscillation when pivoted about either of two points of unequal distances from the center of mass, show that the length of the simple pendulum with the same period is equal to the sum of separations of the pivot points from the center of mass. Such a physical pendulum, called Katter’s reversible pendulum, at one time provided the most accurate way (to about 1 part in 105) to measure the accelerations of gravity discus the advantages of Katter’s pendulum over a simple pendulum for such a purpose.