Answer to Question #165517 in Physics for chelle

Question

1. What are the things to be considered in describing the motion of a physical pendulum? The mass of the object, gravity and axis of rotation.

Answer 1

In this case, a rigid body – instead of point mass - is pivoted to oscillate as shown in the figure. There is no requirement of string. As a result, there is no tension involved in this case. Besides these physical ramifications, the working of compound pendulum is essentially same as that of simple pendulum except in two important aspects :

1) Gravity acts through center of mass of the rigid body. Hence, length of pendulum used in equation is equal to linear distance between pivot and center of mass.

2) The moment of inertia of the rigid body about point suspension is not equal to "mL²" as in the case of simple pendulum.