Physics
posted by Elisa .
A simple pendulum is 9.00 m long.
(a) What is the period of simple harmonic motion for this pendulum if it is hanging in an elevator accelerating upward at 2.00 m/s2?
I keep getting 6.7, but it's wrong

If it is accelerating upward at that rate, the effective value g is
g' = g + a = 11.8 m/s^2
instead of 9.8 m/s^2.
The period will be 2 pi sqrt(L/g')= 5.48 s
Apparently you used g' = g  a. That only applies if the elevator is accelerating downwards.