Final answer:
The force of the opposing force (F) is equal in magnitude and opposite in direction to the applied force (20N).
Step-by-step explanation:
The force of the opposing force (F) is equal in magnitude and opposite in direction to the applied force (20N). According to Newton's first law of motion, an object that is moving with a constant velocity has a net external force of zero. Since the applied force of 20N is the only force acting on the object, the opposing force must also be 20N, but in the opposite direction.