A hockey puck coasts the length of the rink with nothing touching it from behind. You judged the claim that a force keeps it moving: not correct. That leaves the real question. If no force keeps it moving, what does?
You met inertia: an object tends to keep its current velocity, and mass measures that tendency. Inertia is the whole answer here.
Velocity is not used up as an object moves. Moving spends nothing.
A coasting puck needs no forward force to keep moving, because an object's velocity persists on its own (inertia); forces are needed only to change velocity, not to maintain it.
So a force answers only one kind of question: why did the velocity change?
A real coasting puck does slow a little. Slowing is a change in velocity, so a force must be acting.
That force is friction: the ice touches the puck and acts backward on it.
The puck slows only because friction acts on it, not because a force of the shot ran out.
A shuffleboard disk glides down the court and slowly loses speed. Why does it slow?
Remove the friction and the story changes: on perfectly frictionless ice, the puck would keep its velocity with no force acting forward on it at all.
Fay says: on an air-hockey table with the air on, the puck barely slows, because the air cushion almost removes friction and the puck's velocity persists on its own. Is she correct?
A train car rolls at a steady velocity on a straight, level track with negligible friction. What keeps its velocity constant?
A marble rolls over a polished floor and takes a long time to slow down. Over a rough rug it slows almost at once. Explain the difference.
The marble's velocity persists on its own; only a force changes it.
The polished floor exerts very little friction on the marble, so its velocity changes slowly.
The rug exerts much more friction on the marble, so its velocity changes quickly.
The two surfaces differ only in the friction they exert. The marble's tendency to keep its velocity is the same on both.
A canoe coasts over a still lake and slowly loses speed. Why?
The same canoe again, now imagined on water that exerts no resistance at all. What would its motion be after the paddling stops?
Which general statement is correct?