Graphs are used to give a visual orientation of the data collected in an experiment. It is a similar way to display the end result and the relations discovered.
To start the graph, put a title at the top that describes the experiment and the variables. On the x-axis, or the horizontal axis, is the independent variable and on the y-axis, or the vertical axis, is the dependent variable. Make sure each is labeled with the name and the units. When numbering the axis, make sure to start from zero at the origin and that each axis is numbered consistently. After plotting the points of data, the graph should start to take a shape. Check your y-intercept, the point when the independent variable is zero. If it makes sense for the intercept to be (0,0) and it isn’t, there might just have been a small error causing it not to be (0,0). Also, it is important to decide if the relationship is indirect or direct and to find the slope if possible. Indirect means that one variable increased while the other decreased and direct means that the both did the same thing. To find the slope, if it is a line, use the equation: y2-y1/x2-x1 putting in two of the line’s points. After finding the slope decide what it means. Areas of graphs can also be useful. For example, the area of a velocity vs. time graph is equal to the displacement.
Sometimes an equation is needed to describe a line, y=mx+b. The equation can be written in specific form, general form, or in only units.

  • Y Ξ dependent variable
  • M Ξ slope
  • X Ξ independent variable
  • B Ξ y-intercept

Direct or Indirect?

DIRECT RELATIONSHIP= a relationship between two variables in which an increase in the independent variable results in an increase in the dependent variable.
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external image Velocity.gif

INDIRECT RELATIONSHIP= a relationship between two variables in which an increase in the value of the independent variable results in a decrease in the value of the dependent variable
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external image 220px-Simple_inverse_relationship_chart.svg.png

Graph Equations

When writing the y=mx+b equations, there are three ways to do it:
Lets say the graph we are analyzing a graph has a y- intercept of 0m and a slope of 5m/s


When you write a general equation, you use the names of the independent and dependent variable as shown: D=d/t*t+d
(distance= distance over time * time, plus distance)

When you use the specific equation, it will have the exact values substituted in for the variables. So we put d= 5m/s(t)+0m.
which means distance=5 meters per second (time)+ 0 meters.

If we were to write a unit equation, it would go like this: m=m/ss+(m). The Y's unit is meters, the slope is meters over seconds, x is seconds, and b is meters. Since the intercept is 0, it can be left off. We know this equation works because the seconds cancel out, leaving a simplified equation of m=m.