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Vectors
Chapter 3
Vectors
!
If a particle moves in a straight line, we can describe its
position with a single number
x
"
we can keep track of direction by the sign
!
For motion in
3D
, there are
>2
choices of direction
9/8/2009
Lecture 03 – Vectors
2
"
we must then use a
vector
!
A
vector quantity
is something that has both a
magnitude
and a
direction
"
2 km N
,
20 km/h S
past the NCB
!
By contrast, a
scalar
has only a magnitude (with sign)
"
20 km/h
,
–24 °C
Vector Addition/Subtraction
!
We can think of a vector as a
set of instructions
:
"
go 2 km NW
!
Since the starting point isn’t
specified, it is easy to add vectors
just move the beginning of the
9/8/2009
Lecture 03 – Vectors
3
"
2
nd
vector to the end of the 1
st
!
Subtraction is just adding the opposite
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Vector Components
!
It is often useful to split the vector
into two separate instructions:
"
go 1.414 km N, then 1.414 km W
!
This is called
resolving
the vector
into components
9/8/2009
Lecture 03 – Vectors
4
into components.
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 Spring '11
 Singh
 Physics

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