Chapter 5 - Force and Motion-I - Problems - Page 117: 17c

4.9 $m/s^2$

If the cord is cut, there is no longer a Tension so the only force acting in the x direction (along the plane) is that of Fg,x. In part a we found that this is equal to Fgsin(30) = 41.7N. This is the force propelling the block down the ramp and since the block has a mass of 8.5kg and F = ma then a = F/m so a = 41.7N/8.5kg = 4.9 $m/s^2$