Question

What is the moment of inertia of a pendulum with a mass of `3 kg` that is `1 m` from the pivot?

Answer 1

`3 Kg.m^2`

Explanation:

Here,you will have to consider that the bob of the pendulum is a point mass,because its radius is not given.

so,the given situation comes out to be that a mass of `3Kg` is placed`1 m` away from a point,so its moment of inertia w.r.t that point will be `mr^2` or `3 Kg.m^2`

if,the radius of the bob was given as`r`,its moment of inertia w.r.t a diameter would be `2/5mr^2` (bob is actually a sphere)

so,distance between the centre of the bob and the pivoted point would become `(1+r)`

hence,w.r.t the pivoted point moment of inertia would have been`( 2/5mr^2 + m(1+r)^2)`