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How Science Works

The Relationship between Variables.

The way that the variables change
is called the relationship between the variables.
The relationship can be linear,
directly proportional, inversely proportional or non-linear.

Linear just means that the two variables give a straight line graph.
For example, the distance - time graphs of a stationary object
and an object moving with constant velocity are both linear.

Directly proportional means that the rate of increase in one
variable is the same as the rate of increase in the other variable.
If you double one thing, the other thing doubles. For example,
the braking distance of a car is directly proportional to its mass.
The resistance of a wire is directly proportional to its length.

Inversely proportional means that the rate of increase
in one variable is the same as the rate of decrease
in the other variable. If you double one thing, the other
thing halves. For example, the resistance of a wire is
inversely proportional to the cross-sectional area of the wire.

Non-linear means that the rate of increase in one variable
is not the same as the rate of increase in the other variable.
For example, the braking distance of a car
has a non-linear relationship to its velocity.
Enzyme activity has a non-linear relationship to temperature.

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