Well there are 2 ways to move your entity:

1. without physics.
2. with physics

for 1., u move the entity based on cordinates, distances, relative directions, etc., and the entities perform collision detections if u use c_move

but when u want to move an entity with physics, the its the force applied to it and the direction of the force that makes it move and the motion will be based on the physics parameters u set for that entity and also perform collisions in between the movement.

well, for snooker, the rule is not click a point and make ball move to that part. but instead u hit the cue ball with a force in a particular direction. so u need to apply a local force to the cue ball in a direction and the ball will move with all its physics parameters, taking care of the balls in between.

even if u want point and click, u need to calculate the direction from cue point to the clicked position. and apply the force on the ball in that direction.