Question

When a wodden bob is replaced by alluminim one?

Answer 1

As you know, time period of simple pendulum , T = 2π√l/g

Where l is length of bob of simple pendulum.

g is acceleration due to gravity.

here it is clear that time period of siimple pendulum doesn't depend on mass of bob or material property of bob. it just depends on length of bob and acceleration due to gravity .

so, if we replace the wooden bob by identical bob of aluminium, time period remains constant.