Let's review what Newton's second law is: the acceleration of an object is directly proportional to the acting force, inversely proportional to the mass of the object, and directly proportional to the reciprocal of the mass of the object; The direction of acceleration is the same as that of acting force. Formula: F=ma explains the relationship between resultant force f and acceleration a.

Practical application in life: when an object is pushed or pulled, the acceleration is obtained instantly. When the football starts to move, the acceleration changes, thus changing the state of motion.