Final answer:
To find the net horizontal force on a boat with two opposing forces, subtract the smaller force from the larger force, resulting in a net force of 20.0 N.
Step-by-step explanation:
The student's question asks about calculating the net horizontal force on a boat when two opposing forces are applied to it. When two forces are exerted in opposite directions, the net force is the difference between the two forces because they are working against each other. Since the forces acting on the boat are 180.0 N and 200.0 N, respectively, we subtract the smaller force from the larger force to find the net force.
The magnitude of the net force is simply 200.0 N - 180.0 N, which equals 20.0 N. Therefore, the correct answer is D. 20.0 N, showing that the boat would experience a net force in the direction of the larger force, but reduced by the magnitude of the smaller force.