Motion

In order to describe motion we must be able to describe/measure
(qualitative vs quantitative) an object's position Definition of motion
the straight-line distance and direction from a reference point to some
object.

Motion involves the movement from one position to another to describe
an object's position you need
a) a point of reference (an origin)
b) units of distance with which to measure
c) a way of measuring the distance
d) a direction

A point of reference (an origin) this point is called the origin. Usually
designated with a zero (as in x=0) since that is the starting point of counted
off distance from it.

Units of distance
1) an agreed upon standard unit of distance is required in our historical
past, we have used imperial units such as the inch, foot, yard, mile etc.
Scientists all over the world (except USA) use the SI (metric units) to
measure distances. The standard is the metre.

Ways of measuring Distances
Direct measurement: this involves placing a standard unit of length end
to end repetitively until the distance between two points can be judged
(a tape measure) or metre stick can be used.

Indirect Measurements
this is often used for very large of small distances. It involves measuring
one thing and then using geometry or some mathematical approach (trigonometry)
to determine the larger or smaller distance you wish to find it may mean
sending out a signal and timing the return, then calculating the distance of travel.

Eratosthenes [air-a-toss-then-eze]
is the man who first measured the world, a Greek astronomer.

A direction in a one dimensional system of notation using numerical
descriptors for position the direction from the reference point is considered
to be positive (+) or negative (-)

Distance vs displacement
Position as we have previously described determindes the place in space
that an object occupies the mathematical symbol which pysicists commonly
use to describe a position is x

for example: an object located at x=4.5m would indicate an object located
at a position 4.5m in a positive position from the origin (soem reference
point) an object located at a position described by x=-2.2m would
indicate an object located 2.2m from the reference point in a negative
relation.

*Motion involves changing an object's position in space.

Distance
distance refers to the length of the path that an object follows when
it changes position. The odometer in a car records the distance travelled.
it does not record the change of position that the car makes. If you get
in a car and go to the store and back the odometer will have a distance
travelled but the position of the car at the end of the trop is the same
as when it started (at the origin)

Distance
path length is what mathematicians call a scalar quantity it has a magnitude
(amount) but it is not directional.