Consider the classical physics problem of a cube sitting atop a frictionless inclined plane. Of course, this cube will accelerate down the plane with acceleration dictated by F = mgsin(theta), where theta is the angle between the inclined plane and the horizontal surface. Easy enough. Now, my question is this; if the inclined plane was itself sitting atop a frictionless, horizontal plane, would it too accelerate in some direction as the cube slides down its surface? In order to conserve momentum, for instance?