# What is the moment of inertia of a pendulum with a mass of #5 kg# that is #3 m# from the pivot?

##### 1 Answer

45

#### Explanation:

Just use the definition of moment of inertia

To appreciate this definition, take a look at its kinetic energy at any given constant,

Since a pendulum swings back and forth, you can measure/observe two kinds of speeds, the speed of the blob (v) and the speed of the angular change over time (

Then

Let

From an utility point of view, it is much easier to measure the angular change over time (

And of course, you can use the concept of angular momentum to appreciate the definition of