Question

What are tge statements after drawing the graph

Answer 1

technique in experimental physics. Graphs provide a compact and efficient way of displaying the functional relationship between two experimental parameters and of summarizing experimental results. Some graphs early in this lab course should be hand-drawn to make sure you understand all that goes into making an effective scientific graph. You will also learn how to use a computer to graph your data.When graphs are required in laboratory exercises in this manual, you will be instructed to "plot A vs. B" (where A and B are variables). By convention, A (the dependant variable) should be plotted along the vertical axis (ordinate) and B (the independent variable) should be along the horizontal axis (abscissa). Following is a typical example in which distance vs. time is plotted for a freely falling object. Examine this plot carefully, and note the following important rules for graphing:



Figure 1

Graph Paper

Graphs that are intended to provide numerical information should always be drawn on squared or cross-section graph paper, 1 cm × 1 cm, with 10 subdivisions per cm. Use a sharp pencil (not a pen) to draw graphs, so that the inevitable mistakes may be corrected easily.

Title

Every graph should have a title that clearly states which variables appear on the plot. Also, write your name and the date on the plot as well for convenient reference.

Axis Labels

Each coordinate axis of a graph should be labeled with the word or symbol for the variable plotted along that axis and the units (in parentheses) in which the variable is plotted.

Choice of Scale

Scales should be chosen in such a way that data are easy to plot and easy to read. On coordinate paper, every 5th and/or 10th line is slightly heavier than other lines; such a major division-line should always represent a decimal multiple of 1, 2, or 5 (e.g., 0, l, 2, 0.05, 20, 500, etc.). Other choices (e.g., 0.3) make plotting and reading data very difficult. Scales should be made no finer than the smallest increment on the measuring instrument from which data were obtained. For example, data from a meter stick (which has 1 mm graduations) should be plotted on a scale no finer than 1 division = 1 mm. A scale finer than 1 div/mm would provide no additional plotting accuracy, since the data from the meter stick are only accurate to about 0.5 mm. Frequently the scale must be considerably coarser than this limit, in order to fit the entire plot onto a single sheet of graph paper. In the illustration, scales have been chosen to give the graph a roughly square boundary; you should avoid choices of scale that make the axes very different in length. Note in this connection that it is not always necessary to include the origin ('zero') on a graph axis; in many cases, only the portion of the scale that covers the data need be plotted.

Data Points

Enter data points on a graph by placing a small dot at the coordinates of the point and then drawing a small circle around the point. If more than one set of data is to be shown on a single graph, use other symbols (e.g. θ, Δ) to distinguish the data sets. A drafting template is useful for this purpose.

Curves

Draw a simple smooth curve through the data points. The curve will not necessarily pass through all the points, but should pass as close as possible to each point, with about half the points on each side of the curve; this curve is intended to guide the eye along the data points and to indicate the trend of the data. A French curve is useful for drawing curved line segments. Do not connect the data points by straight-line segments in a dot-to-dot fashion. This curve now indicates the average trend of the data, and any predicted values should be read from this curve rather than reverting back to the original data points.

Straight-line Graphs

In many of the exercises in this manual, you will be asked to graph your experimental results in such a way that there is a linear relationship between graphed quantities. In these situations, you will be asked to fit a straight line to the data points and to determine the slope and y-intercept from the graph. In the example given above, it is expected that the falling object's distance varies with time according to 

d = 12gt2. 

 It is difficult to tell whether the data plotted in the first graph above agrees with this prediction. However, if d vs. t2 is plotted, a straight line should be obtained with slope = g/2 and y-intercept = 0.

Straight Line Fitting