Final answer:
Kinetic friction is the force acting on a shuffleboard disk sliding on a rough surface, which is an external force opposing the disk's motion.
Step-by-step explanation:
When a shuffleboard disk slides to the right on a rough surface, the force acting on it is kinetic friction. Friction is a resistive force that opposes motion, meaning it acts in the opposite direction to which the disk is moving. According to Newton’s First Law of Motion, which is often associated with the concept of inertia, kinetic friction is an external force because it arises from interactions with the surface the disk is moving over.
The magnitude of kinetic friction depends on two factors: the coefficient of kinetic friction and the normal force. The normal force is always perpendicular to the surface, and if there is no vertical motion, it balances out the gravitational force exerted on the object. Since the disk is sliding horizontally, the kinetic friction can be calculated using the equation f_k = μk N, where f_k is the kinetic frictional force, μk is the coefficient of kinetic friction, and N is the normal force.