Newton's Second Law of Motion and Physics

Newton's 2nd Law of Motion states that a mass acted on by a force undergoes acceleration in the direction of the force, with a magnitude inversely proportional to the mass and proportional to the force.

Newton's 2nd Law shows that a force being applied to a mass produces a steady increase in speed. Furthermore decreasing the mass and increasing the force produces a faster increase in speed and increasing the mass and decreasing the force produces a slower increase in speed.

All changes in motion are based on Newton's 2nd Law including changes in speed and direction. It is indeed fundamental to understanding of motion since without it changes in motion can not be properly understood.