The block of mass $m$ slides on a wedge of mass $m$ which is free to move on the horizontal ground. Find the acceleration of wedge and block.
Let $a$ be the acceleration of the wedge and $b$ be the accleration of the block with respect to the wedge. Applying Newton's laws of motion in $x$ direction,
But why is $F_x=0$. If it is true, then how can a system can have acceleration in $x$ direction(also they are not massless)?