Dynamics is a branch of physical science and subdivision of mechanics that is concerned with the motion of material objects in relation to the physical factors that affect them: force, mass, momentum, energy.
Dynamics can be subdivided into kinematics, which describes motion, without regard to its causes, in terms of position, velocity, and acceleration; and kinetics, which is concerned with the effect of forces and torques on the motion of bodies having mass. The foundations of dynamics were laid at the end of the 16th century by Galileo Galilei who, by experimenting with a smooth ball rolling down an inclined plane, derived the law of motion for falling bodies; he was also the first to recognize that force is the cause of changes in the velocity of a body, a fact formulated by Isaac Newton in the 17th century in his second law of motion. This law states that the force acting on a body is equal to the mass of the body multiplied by the acceleration.
Excerpt from the Encyclopedia Britannica without permission.