Kinematics Terminology - Teacher

brontidegrrrMechanics

Nov 14, 2013 (3 years and 7 months ago)

78 views

Kinematics Terminology


Kinematics
:

Study of motion of objects


Scalar
:

a number (measurement) that has units

eg: temperature 20 C, height 180cm, speed 40 km/h,
time 30 min.


Vector
:
a number (measurement) that has units and a direction


eg: veloc
ity 100 km/h [E], position 25m[W]


Acceleration 5m/s
2

[S]




Distance, Position, Displacement


Distance

is the length of a path taken by an object as it moves
from one location to another. Distance is a scalar quantity
since direction is irrelevant.


Pos
ition

is the location of an object with reference to a specific
location. Position is a vector quantity since a direction
must be stated, usually in square brackets.


The SI Unit of measurement for length is the metre.

d=distance

Scalar distance walked t
o school 2 km

d=position


Vector (direction) 1 km[E] then 1 km[S]

* arrow on top of measurement variable indicates vector



Displacement

is the
net difference in position

from the start
location of the object to the end location. Displacement is
a vecto
r quantity since it comes from difference in position,
which has a direction.

d= 1.4 km[SE]




Drawing Vectors


Must show your reference coordinates and indicate
a scale 1 cm=1 m or 1 cm=5 km etc.


Always use a ruler to draw the appropr
iate length of vector and
a protractor to indicate the exact direction.


Eg: d=10 km [E]



(line is 2 cm long using scale 1 cm=5 km)





Negative Vectors


8 km [W] =
-
8 km [E]



-
8
-
7
-
6
-
5
-
4
-
3
-
2
-
1 0 1 2 3 4 5 6 7 8










We can multiply a vector by scalar; the magnitude changes but
the direction does not.