Non-inertial frame of reference

[rrosa522]

Homework Statement

You use a string to suspend a cork ball with a mass of 22.0g from the ceiling of a moving speedboat. The ball and string hang at 32.5 degrees from the vertical. Calculate the acceleration of the speedboat.

Homework Equations

The Attempt at a Solution

I was able to calculate using inertial frame of reference and I got 6.2m/s^2, which is the correct answer. But my teacher wants me to use non-inertial frame of reference to answers this question and I have no idea how.
My teacher said that the acceleration of the speedboat is equal to the fictitious force, but I found the fictitious force and it did not equal to 6.2

 

[Doc Al]

My teacher said that the acceleration of the speedboat is equal to the fictitious force, but I found the fictitious force and it did not equal to 6.2

The fictitious force equals ma, not a. (An acceleration would not even have the correct units.)