First, we need to determine the ratio between two physical quantities. This ratio can be a numerical relationship between two physical quantities or a unit relationship between two physical quantities. For example, if we want to express the relationship between the speed and time of an object, we can define the speed as the distance that the object moves in unit time, that is, speed = distance/time. In this way, we can get that the ratio of speed to time is a constant.
Next, we can use the coordinate system in the mathematical chart to represent the relationship between these two physical quantities. In the two-dimensional coordinate system, we can take one physical quantity as the abscissa and the other as the ordinate. Then, we can draw a straight line from the known data points. The slope of this straight line is the ratio of two physical quantities.
By observing this straight line, we can get some useful information. First, we can see the direct ratio between two physical quantities. Secondly, we can determine the ratio between two physical quantities by the slope of a straight line. Finally, we can also determine the value of a physical quantity when it is 0 by the intercept of a straight line.
In a word, mathematical chart is a very effective tool, which can be used to express the direct proportional relationship of physical quantities. By drawing a straight line, we can intuitively observe the proportional relationship between two physical quantities and determine the ratio and intercept between them. This is very helpful for understanding and analyzing physical phenomena.