If you push something it moves, and if you push it harder it moves faster. If you keep pushing it it will be faster and faster.. it will accelerate in fact, and the acceleration will be proportional to the force you apply.

The explanation above is very simplistic. It ignores all other forces apart from the applied force. In fact there will be other forces acting, most commonly friction, and we must find the net force F before we use F=ma to calculate the acceleration.

The ball above is falling. The net force F is W-R. If m=5 Kg and R=20N then applying F=ma:The block above is being pulled along the ground. The resultant force F is P-R. If P=30N, R=10N and m=2 Kg then applying F=ma: