Question

what is meant by second's pendulum

Answer 1

A second pendulum  is 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. A pendulum  is a weight suspended from a pivot so that it can swing freely....

Answer 2

A seconds pendulum is a pendulum whose period is precisely two seconds.One second for swing in one direction and one second for return swing.