Ch. 2 – Kinematics in 1-D
Mechanics
Kinematics
Dynamics
Concepts needed to describe
motion w/o forces
Deals with the effects that forces
have on motion
Chs. 2 and 3
Ch. 4
Our goal is to describe the motion of some object.
To do this, we must be able to specify its location in space at all times!
In other words, what is the position of some object at time
t
?
Define
Displacement
:
A vector
which points from an object’s initial position to its final position.

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In this chapter, we will only consider 1 dimensional motion.
Let’s look at the
following
example
:
At time
t
=
t
a jogger’s position relative to some fixed origin is
x
At some later
→
At time
=
o
, a jogger s position relative to some fixed origin is
o
.
At some later
time,
t
=
t
f
, her position relative to the origin is
x
f
.
What is her displacement during
this time interval?
→
t
=
t
o
t
=
t
f
→
x
origin
x
o
→
x
f
→
Δ
x
Her displacement,
Δ
x
,
is the difference in her initial and final positions.
→
→
→
Displacement =
Δ
x
=
x
f
–
x
o
→
Δ
x
is pronounced “delta x”, or “change in x”.
→
Units?
The SI unit of displacement is the meter (m).
In 1-D we can also talk about
scalar displacement
, which is just a number.
It
can be either positive or negative.
→
→
For example, in the above problem, if
x
o
= 10 m and
x
f
= 30 m, then her scalar
displacement would be positive 20 m.