Final answer:
The net force on an object when two forces are applied depends on whether the forces are acting in the same, opposite, or perpendicular directions. For forces in the same direction, add them; for opposite, subtract. Directions are needed for an exact answer.
Step-by-step explanation:
To calculate the net force acting on an object when two forces are applied, you need to determine if the forces are acting in the same direction, opposite directions, or perpendicular to each other. In this case, the student has not specified the directions of the forces, however, typically if they are in the same or opposite directions, you will add them (if in the same direction) or subtract them (if in opposite directions). If the situation given by the student was similar to the reference where a 20N and a 15N force act on the object, assuming they act in the same direction, we would simply add: Fnet = 20N + 15N = 35N. If they acted in opposite directions, the net force would be Fnet = 20N - 15N = 5N. Without the specific directions, we cannot provide a precise net force.