physics
posted by Elisa on .
A simple pendulum with a length of 1.50 m is suspended from the ceiling of a train. What is the period of simple harmonic motion for the pendulum if the train is moving up an incline of 15.0˚ with an acceleration of 3.00 m/s²?
Don't know how to do, please help

The pendulum will act as if the gravitational acceleration were the vector sum of g (down) and a, aimed 15 degrees below horizontal. Call the resultant g'
g' = sqrt (g^2 + a^2  2 ag cos 105) = 10.96 m/s^2
Then use g' instead of g in the formula for the period.
P = 2 pi sqrt (L/g')
Just adding the vertical component of a to g will not get you the right answer for g'.