(20 10? Luzhou) as shown in Figure A, it is a belt conveyor for transporting coal in a factory, and Figure B is a simplified schematic diagram of its working process, in which the rotating wheels driv

(20 10? Luzhou) as shown in Figure A, it is a belt conveyor for transporting coal in a factory, and Figure B is a simplified schematic diagram of its working process, in which the rotating wheels drive the horizontal belt at a uniform speed. (1) The conveyor belt moves to the right at a constant speed. When the coal block is just put up, it changes from static to right, and there is no other pull or thrust in the horizontal direction, but only friction to the right.

(2) When the coal block moves in a straight line at a uniform speed, it is either not stressed or unbalanced. When the coal block moves to the right at a uniform speed, if it is subjected to friction in the horizontal direction, there must be another force to balance it, because there is no other force, so it is not forced;

(3) When the conveyor belt is braked, the coal block moves from right to rest, and only when the friction direction is left can the coal block be prevented from moving further to the right.

So the answer is: to the right; Zero.