If there is a body in a non-inertial reference frame (say accelerating with acceleration $A_1$) and an observer in another non-inertial reference frame (say accelerating with acceleration $A_2$) what would be the pseudo-force acting on the body (say it has mass $m$) as seen by the observer? Both $A_1$ and $A_2$ are in the same direction and along a straight line.
Do I simply need to find the relative acceleration of the first frame with respect to the second frame and multiply the relative acceleration with the mass of the body?