Five 2.0 kg blocks are arranged as shown on a horizontal surface that the bottom blocks slide on without friction; and there is no friction at the vertical faces of the bottom blocks where they are smacked together. There is however friction at the horizontal faces of the stacked blocks where they are touching, in fact, enough so that the stacked blocks stay arranged as shown while all the blocks move together to the right faster and faster. And the reason the blocks are moving to the right faster and faster is because a hand is pushing 10 N horizontally to the right on the block at the bottom left of the arrangement; and it is the only thing touching the blocks other than the surface.