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====Positive and Negative Direction====
: When two [[force]]s act in opposite directions, along a line, one direction is chosen to be a [[Positive (Number)|positive]] direction and the other is chosen to be a negative direction, just as on a [[Number Line|number line]] in [[maths]].
{| class="wikitable"
|-
|[[File:ForceNumberLineVertical.png|center|200px]]
| style="height:20px; width:300px; text-align:center;" |If the 'up' direction is chosen to be [[Positive (Number)|positive]] then any [[vector]] pointing 'up' has a [[Positive (Number)|positive]] value and any [[vector]] pointing 'down' has a negative value.
In this [[diagram]] the green [[vector]] has a value of +2 while the red [[vector]] has a value of -4.
|[[File:ForceNumberLineHorizontal.png|center|400px]]
|-
| style="height:20px; width:400px; text-align:center;" |If the 'right' direction is chosen to be [[Positive (Number)|positive]] then any [[vector]] pointing 'right' has a [[Positive (Number)|positive]] value and any [[vector]] pointing 'left' has a negative value.
In this [[diagram]] the blue [[vector]] has a value of +3 while the yellow [[vector]] has a value of -2.