What happens to the block on an inclined plane when the pushing force is removed?

When the pushing force is removed from a block on an inclined plane, the block will begin to slide back down the incline due to the force of gravity acting on it. This is because, once the external pushing force is eliminated, the only forces acting on the block are its weight and the normal force from the inclined surface.

The weight of the block can be broken down into two components: one acting perpendicular to the inclined surface (which is countered by the normal force) and one acting parallel to the incline, pulling the block down the slope. If the machine is not self-locking, there are no additional forces holding the block in place, making it vulnerable to gravitational pull. Hence, it will start to slide down the incline, indicating that the block's motion is governed by the force of gravity that takes over when the external pushing force is no longer applied.

This understanding highlights the crucial role that unbalanced forces have in determining the motion of objects on inclined planes.