the time T in second for a pendicular of length L feet to make one swing is given by t =2pie square root L over 40
How long is the perpendicular if it makes 1 swing in 1.9 second use 3.14
well, you have the formula:
t = 2π√(L/40)
just plug in your t and find L.
by the way, the word is pendulum, not either of the garbled attempts you wrote.