The force constant of a spring is 800 N/m and the unscratched length is 0.63 m. A 4.6 kg block is suspended from the spring. An external force slowly pulls the block down, until the spring has been stretched to a length of 0.76 m. The external force is then removed, and the block rises. When the spring has contracted to a length of 0.66 m, the acceleration of the block, including direction, is closest to?