PHYSICS · Multi-part · A Level · Physics · Mechanics and materials · Mechanics and materials
Problem
A hockey puck glides across a perfectly smooth, horizontal sheet of ice at a constant speed. Air resistance is negligible, and the puck is not in contact with any object except the ice.
A student is asked to construct a complete free-body diagram (FBD) for the puck and to defend the forces included on the diagram.
(1) Part (a)
Identify every force acting on the puck and state whether each force is a contact force or a non-contact force.
(2) Part (b)
Describe why no additional forces—such as a "force of motion" in the forward direction—should appear on a correct FBD for this situation, even though the puck is moving across the ice.
(3) Part (c)
Explain how your FBD is consistent with the observation that the puck’s velocity remains constant while it is on the smooth ice.