Electrostatic force upon a particle within a uniform electric field.

Kinematics represents a set of tools for describing motion. When we progress from kinematics to Newton''s laws, the concept of force enters the discussion. This is a big transition. In kinematics, you discuss how an object is accelerating. In Newton's laws, you discuss why the object is accelerating. Kinematics is about describing motion. Newton's laws is about describing interactions.

In Newton's laws, you learn that if an object is accelerating, a net force must be acting upon it. In other words, there is an interaction. The kinematics of an object results from its dynamics (the interactions of the object and other objects in its surroundings). Newton's 1st and 2nd laws are directly concerned with the relationship between motion and force. Every acceleration is caused by a force, a favorite idea for MCAT questions of a certain type. If a particle is accelerating, a force must be acting on it. If there is no net force, it will either be at rest or moving with constant velocity.