ACCELERATION FROM NET FORCE

Newton's second law states that the net force acting on an object equals its mass multiplied by its acceleration: F = ma. Here the surface is frictionless, so the only horizontal force is the applied 30 N push. There is no opposing friction to subtract. The net force is therefore exactly 30 N. Rearranging the second law gives a = F/m. Substituting the known values: a = 30 N ÷ 5 kg = 6 m/s². The direction of the acceleration matches the direction of the force — the box speeds up in the direction it was pushed. This is the purest expression of the second law: one force, one mass, one acceleration. The number 6 m/s² means that every second the box is gaining 6 metres per second of speed. In two seconds it would be moving at 12 m/s; in three seconds, 18 m/s — and so on, for as long as the force is applied. A common error is to confuse the box's weight (mg = 5 × 9.8 ≈ 49 N) with the applied force. Weight acts downward and is balanced by the normal force from the surface; it plays no role in the horizontal acceleration. Another trap is inverting the fraction and computing m/F = 5/30 ≈ 0.17, which gives units of kg/N — not m/s².