Vector diagram showing how an object traveling in uniform circular motion moves off at a tangent once there is no centripetal force.
As we move from Kinematics, in which we discussed HOW
objects move to Dynamics, in which we discuss WHY
, let us reprise the primary conceptual movement from Kinematics to Dynamics.
Force is a concept of Dynamics. Acceleration is described in Kinematics. Under the influence of a net force an object accelerates. Its velocity changes, speeding up, slowing down, or changing direction.
Net force and acceleration always exist together. If an object is accelerating, a net force must be acting upon it. Almost every MCAT has some question that turns on your comfort with the idea that acceleration does not occur without a force. If there is no force, the object maintains constant velocity.