Is there any effect on inertia of a bar pendulum if extra mass added to it?

Answer 1

Yes, it does.

If a pendulum has more weight, it travels faster down, therefore travelling further once past 90 degrees.

e.g. In the tower that holds the famous bell, Big Ben, in London, the pendulum that makes the clock on the clock tower's hands move, has coins placed upon the butt, to get the exact swing the correct speed. It is measured every week, to see if it is going to fast (too much weight), or too slow (more weight needed). So, according to the results, they either add, or subtract coins from the but of the pendulum.

Answer 2

Adding extra mass to a bar pendulum will increase its inertia, as inertia is directly proportional to mass. This will affect the swinging motion of the pendulum by making it harder to set in motion and slowing down its oscillations.