Newton's First and Second Laws of Motion

Newton's First Law states that an object in motion will continue moving at constant speed in a straight line unless acted upon by a resultant (unbalanced) force. The puck is slowing down, so an unbalanced force must be acting on it.

Friction is the force that opposes the relative motion between two surfaces in contact. The ice surface exerts a frictional force on the puck in the direction opposite to its motion, acting as the unbalanced force that decelerates it.

It is a common misconception that objects need a continuous force to keep moving. According to Newton's First Law, this is incorrect — objects only stop because an opposing force (like friction) acts on them, not because the forward 'force' runs out.

The correct explanation is that friction from the ice surface acts as an unbalanced force, decelerating the puck. This is fully consistent with Newton's First Law.

The question asks why the puck stops, requiring us to identify the correct physical explanation using Newton's Laws.

The option stating that 'moving objects always need a force to keep them moving' directly contradicts Newton's First Law. This is the classic misconception the law disproves — eliminate it.

The idea that the puck 'loses its forward force' is also a misconception. After the stick leaves the puck, there is no forward force — the puck was already maintaining speed by inertia. Eliminate this option.

Gravity acts vertically downward and is balanced by the normal reaction force from the ice. Gravity does not directly stop horizontal motion on a flat surface. Eliminate this option.

The remaining option — friction from the ice surface acts as an unbalanced force, decelerating the puck — is correct. Friction is the opposing force responsible for the puck's deceleration.