Why might knowing newton's second law be useful in the real world?

Because the second law is acceleration  of an object it helps cars go and people walk..

Gravity, from the center of mass of the box, extending downward normal force, from the floor under the box, extending upward, equal to gravity push force, acting at a point on the box, extending in the direction of motion friction, acting at any point on the box directly opposite the push, extending directly opposite to the motion