5 Usually, we just use the part of the graph that deals with (+) numbers
6 Suppose we wanted to graph a change over a period of time For example, something goes twice as fast every second that it accelerates…It is going 1 m per second (1 m/sec)… when we first see it, at second one,How fast is it going in 2 seconds?...RIGHT: 2 m/sec…How fast in 3 seconds?...RIGHT: 4 m/sec.
7 The data table looks like this: It relates time to speed, andIt allows you to graph data points…Data points are (x,y) pairs,E.g. (1 sec = 1 m/s) is the same as (1,1).
8 TIME AND SPEEDTime varies – second 1, second 2, second 3, second 4, etc.Speed varies – 1 m/sec, 2 m/sec, 4 m/sec, 8 m/sec…Time changes, but we can’t change it. It is an independent variable…But we can change speed, so it is a dependent variable – it is dependent on how long it has been traveling (accelerating).
9 INDEPENDENT & DEPENDENT VARIABLES Usually, the independent variable goes on the x-axis…How many units should we use?...Always label the axis so that people know what the graph is telling them.
10 INDEPENDENT & DEPENDENT VARIABLES The dependent variable usually goes on the Y axis…Both axes often start with 0…We generally only need as many number points as we are going to measure.
11 Then we place our data points Your data points are (x,y) pairs,Plot only one set of data points at a time,Plot another data set after finishing the first set.
12 Finish the data points Connect each dot with a line… The line should show a trend if there is a relationship between the dependent & the independent variable.
13 There are other ways to display the information This graph represents the same data points, but is displayed in the form of bars,Informally, it is called a bar graph,Formally, it is called a histogram.
14 Can we add more data to the same graph? SURE!!Suppose we have another rate of increase of speed…1 m/sec increase…How fast will it be going in 3 seconds?