A question struck my mind when i was trying to solve the following problem,
I was able to solve it by just considering forces in the horizontal and vertical direction however the solution turned out to be very lengthy, i found a solution for it online which used psuedo/fictious forces to solve the problem, the solution was as follows
Suppose there is an observer on the wedge and the wedge is accelerating towards the left with acceleration $a$. Then the psuedo force on the block of mass $m$ is $ma$.
Balancing forces on $m$ normal to the plane we get $$N + ma\sin\theta = mg\cos\theta$$ Balancing forces on $M$ in $X$ direction $$F + N\sin\theta = F\cos\theta + Ma$$
Solving these two equations gives me the solution to the above question as follows
$$a = \frac{mg\sin\theta\cos\theta + F(1-\cos\theta)}{M+m\sin^2\theta}$$
This does match with my answer and with the answer in my textbook, however i do not understand why there would be a psuedo force on the wedge of mass $M$, amounting to $Ma$.
With respect to a observer on the wedge should there be no psuedo force on it?.
Any help would be highly appreciated!