Objectives  Develop position-time graphs for moving objects.  Use a position-time graph to interpret an object’s position or displacement.  Make motion diagrams, pictorial representations, and position-time graphs that are equivalent representations describing an object’s motion.

USING A GRAPH TO FIND OUT WHERE AND WHEN Graphs of an object’s position and time contain useful information about an object’s position at various times and can be helpful in determining the displacement of an object during various time intervals. Position Time Graph – a graph that can be used to determine an object’s velocity and position, as well as where and when 2 objects meet, by plotting the time data on a horizontal axis and the position data on the vertical axis. This graph shows Position (vertical axis) versus Time (horizontal axis). Note: with the graphs you will read the vertical axis per the horizontal axis and this will give you a measurement we use such as Position Time Graph m/s, which is a velocity. Also, Mass versus Volume which is g/cm 3, which is Density, etc.

USING A GRAPH TO FIND OUT WHERE AND WHEN To draw the graph, plot the object’s recorded positions. Then, draw a line that best fits the recorded points. This line represents the most likely positions of the runner at the times between the recorded data points. Example 1 p. 39 Question 1: the runner is at 30 meters after 6 seconds. Question 2: after 4.5 seconds the runner is at 22.5 meters. Do Practice Problems # 9-13 p. 39

USING A GRAPH TO FIND OUT WHERE AND WHEN An instant of time last ZERO seconds. Instantaneous Position – is the position of an object at any instant of time. Example Problem 2 p. 41 B passes A at about 190 meters and 45 seconds. Do Practice Problems # p. 41 As you have seen you can represent the motion of more than one object on a position time graph. The intersection of 2 lines tells you when the 2 objects have the same position. Do 2.3 Section Review