Answer
(a) The block speeds up from 0 to 1.
(b) The block continues to speed up from 1 to 2.
Work Step by Step
(a) The block has a net force $F_x$ that points in the positive x-direction. Therefore, $a_x$ points in the positive x-direction. Therefore, the block speeds up from 0 to 1.
(b) Although the magnitude of the force decreases, the block still has a net force $F_x$ that points in the positive x-direction. Therefore, $a_x$ points in the positive x-direction. Therefore, the block continues to speed up from 1 to 2.