A moving object needs no force at all to keep moving; force is only needed to change its velocity. With friction stripped away entirely, the block drifts on forever without slowing, which is Newton’s first law made visible. The awkward part sits at the border between static and kinetic friction: while the pull stays small, static friction matches it exactly and nothing moves, but past the μₛN threshold the block breaks free and slides on under a smaller kinetic coefficient. That breakaway threshold falls as the surface changes from wood to a smooth floor to ice, so on ice the gentlest pull already sets the block sliding.
A moving object needs no force at all to keep moving; force is only needed to change its velocity. With friction stripped away entirely, the block drifts on forever without slowing, which is Newton’s first law made visible. The awkward part sits at the border between static and kinetic friction: while the pull stays small, static friction matches it exactly and nothing moves, but past the μₛN threshold the block breaks free and slides on under a smaller kinetic coefficient. That breakaway threshold falls as the surface changes from wood to a smooth floor to ice, so on ice the gentlest pull already sets the block sliding.
Related topics in Matter & Atom