When acceleration is along direction of motion, object either accelerate in the direction or decelerate in the direction of motion.
Eg. Car moving in a straight line (linear motion)
When acceleration is in one direction only but not along the direction of motion , parabolic motion is observed.
E.g Electron moving inside a pair of parallel plate or throwing a object in g field
When accceleration is always perpendicular to velocity , resulting in circular motion.
E.g charge particle moving in B field.
