Final answer:
The uncertainty of the x-variable and y-variable is determined by the size of the rectangle on the graph around the plotted points. It represents the range of potential values for the measurements, given as ±mm for the x-variable and ±g for the y-variable.
Step-by-step explanation:
The uncertainty of a measurement in physics is an indication of the precision of that measurement and how much it may vary from the actual or expected value. When two data points are plotted, and the uncertainty is described as the size of the rectangle on the graph, we are trying to determine the range of possible values the x-variable and y-variable could have based on the scale provided by the plot. To calculate the uncertainty for the x-variable and y-variable, generally, you would look at the dimensions of the rectangle that would be drawn around a plotted point to encompass the range of possible values for that point, denoting the marginal error in the measurements on each axis.
In the absence of specific numerical values, we can use an example to illustrate this concept: If the rectangle around a point has a horizontal length of ±2 mm, then the uncertainty for the x-variable, often denoted as Δx, would be ±2 mm. Similarly, if the vertical height of the rectangle is ±5 g, then the uncertainty for the y-variable, or Δy, would be ±5 g.