An astronaut constructs a pendulum with a length of 1 meter on a new planet. If the period is 3.9 second, what is the acceleration due to gravity?

Can someone help me with formulas to determine this?

1 answer

period=2PI*sqrt(l/g)
3.9=2PI*sqrt(1/g)

square both sides.
3.9^2/(2PI)^2=1/g

g=(2pi/3.9)^2