Linear Motion with a Constant Acceleration
Definition of Motion
Parameters for describing motion: Position, Displacement, Velocity and Acceleration
Motion in a Straight line
We describe the motion of an object while ignoring the interactions with external agents that might
be affecting or modifying that motion (This portion of classical mechanics is called
We use what is called the particle model and describe the moving object as a
its size. A single particle of the object represents the whole object.
By the end of this unit, you will be able to;
• Define in scientific terms what motion is.
• Define the velocity and acceleration of a particle undergoing rectilinear motion.
• Distinguish between average and instantaneous velocity of a particle undergoing rectilinear
• State the laws of motion
• solve problems concerning rectilinear motion of objects using the laws of motion
“What is motion”?
An object is said to be in motion if it changes its location at different times. This means that our
study of motion will deal mainly with questions like where and when? Motion may be defined as
a continuous change of position with time.
One dimensional motion is also known as rectilinear motion. Motion of a particle in space is
described by three dimensions Cartesian plane.
Parameters Describing Motion
is the location of the particle with respect to a chosen reference point that
we can consider to be the origin of a coordinate system. The motion of a particle is completely
known if the particle’s position in space is known at all times. Reference position,
± = 0
Consider the table below of position of a car at a given time interval