IN SECONDS PENDULUM,MASS OF BOB IS 30G.IF IT IS REPLACED BY 90G MASS.THEN ITS TIME PERIOD WILL BE

A seconds pendulum is a pendulum whose period is precisely two seconds; one second for a swing in one direction and one second for the return swing, a frequency of 1/2 Hz

It can be shown by calcuiation that in earth where g = 9.81 m/sec²

the length of the seconds pendulum is = 1 metre.

Hence replacement of the bob of mass 30g by a bob of 90g will not change the Time period,it will remain same as before i.e. 2s