A small block rests on a smooth floor. A light string tied to it runs up to a small pulley fixed $1.5\ \text{m}$ above the floor (treat the block as a point on the floor), and its free end is pulled down at a steady $1.0\ \text{m/s}$, as shown in the figure. The block slides along the floor towards the point below the pulley. What is the acceleration of the block at the instant when the string makes $60^\circ$ with the floor?

Fig. 1: A block rests on a smooth floor. A string from the block runs up at an angle theta to the floor, over a small pulley on a fixed post at height h of 1.5 m, and its free end hangs down and is pulled down at u of 1.0 m/s.