Chapter 2
Motion Along a Straight Line
In this chapter we will study kinematics i.e. how objects move along a
straight line.
The following parameters will be defined:
Displacement
Average velocity
Average Speed
Instantaneous velocity
Average and instantaneous acceleration
For constant acceleration we will develop the equations that give us the
velocity and position at any time.
In particular we will study the motion under
the influence of gravity close to the surface of the earth.
Finally we will study a graphical integration method that can be used to
analyze the motion when the acceleration is not constant
(2-1)

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Kinematics
is the part of mechanics that describes the motion of physical
objects.
We say that an object moves when its position as determined by an
observer changes with time.
In this chapter we will study a restricted class of kinematics problems
Motion will be along a straight line
We will assume that the moving objects are “
particles
” i.e. we restrict our
discussion to the motion of objects for which all the points move in the same
way.
The causes of the motion will not be investigated. This will be done later in the
course.
Consider an object moving along a straight
line taken to be the x-axis. The object’s
position at any time t is described by its
coordinate
x(t)
defined with respect to the
origin O. The coordinate
x
can be positive or
negative depending whether the object is
located on the positive or the negative part of
the
x
-axis
(2-2)