Final answer:
To determine the net force on an object, all acting forces must be considered. The net force is the vector sum of these forces, and for an object not accelerating, the net force is zero. Additional context is needed to accurately determine a specific net force on an object.
Step-by-step explanation:
To determine what is the net force acting on an object, we must consider all the forces acting on it and calculate their sum. The net force is the vector sum of all the forces, and if the object is not accelerating, then the net force is zero. In the case of an object in uniform circular motion, there is a net force acting on it because it is accelerating towards the center of the circle, even though its speed might be constant. The net force is always directed towards the center of the path, known as the centripetal force, supporting option 'a' from the information provided.
Considering an example where a man pushes a box across a floor at a constant velocity, if he applies a force of +50 N and there's no acceleration, the force of friction opposing the motion must equal -50 N, yielding a net force of 0N due to the balancing of forces.
Thus, without additional context for the originally stated question, such as which forces are involved or their magnitudes/directions, we cannot accurately answer whether the net force is 0N, 6N, 10N, or 12N. Different scenarios would lead to different net forces based on the forces interacting with the object.