Question

What is a second's pendulum?what is its length?

Answer 1

Seconds pendulums were used in vintage clocks which advanced one second, every time the pendulum reached an extreme position.A seconds pendulum takes exactly 1 second to move from one extreme pendulum takes 2 second to complete one ossiliation or the time period of a seconds pendulum in 2 second.

​​​Since the pendulum reaches its extreme position twice in one oscillation, the time period of a seconds pendulum is 2 seconds.

The time period of a simple pendulum of length L is

T=2π√(l/g)

Put T=2 seconds

g = 9.81m/s^2

L=g/π^2=.994m

On earth, the seconds pendulum has a constant length of approximately 1m