Motion

• One Dimensional Motion. The motion of an object is said to be one

dimensional motion if only one out of the three coordinates specifying the
position of the object changes with respect to times.
(an object moves along any of the three axes X, Y or Z).

•  Two dimensional motion. The motion of an object is said to be two

dimensional motion if two out of the three coordinates specifying the position
of the object change with respect to time. (the object moves in a plane.)

•  Three dimensional motion. The motion of an object is said to be three

dimensional motion if all the three coordinates specifying the position of
the object change with respect to time. (the object moves in space.)

•  Speed. The speed of an object is defined as the ratio of distance covered

and time taken i.e. speed = distance traveled/(time taken). Speed is a
scalar quantity. It can only be zero or positive.

•  Instantaneous velocity. The velocity of an object at a given instant of time

is called its instantaneous velocity. When a body is moving with uniform
velocity, its instantaneous velocity = average velocity = uniform velocity.