A particle of mass m is placed on the smooth face of an inclined plane of mas s M and slope which is free to slide on a smooth horizontal plane in a direction perpendicular to the edge. If the particle slides with an acceleration a, the acceleration of the inclined plane towards right A will be
As the particle moves down the inclined plane, let a be its acceleration. Now the inclined plane moves horizontally towards right with acceleration A.
Considering the vertical component of forces acting on the particle.
For horizontal components the motion of the particle is considered at the accelerated frame. So a horizontal fictious force acts opposite to A. This pseudo force mA acts towards the left.
Now consider the force on inclined plane. The forces are shown in figure.