If the net force on the block is non-zero then the block accelerates. If the net force on the block is zero, then acceleration is zero.
To check whether the particle will have any acceleration or not, let us confirm if net force is zero or not by resolving the forces in both horizontal and vertical directions.
Net force in horizontal direction =4cos30°− 4cos30° = 0
Net force in vertically downward direction = 8 − 4sin30°− 4sin30°≠ 0
The net force is not zero. Therefore, the particle will have downward acceleration.
