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Position-Time Graphs - Conceptual Analysis - help5

The slope of a position-time graph reveals informaiton about the speed of an object. In fact one could generalize that "however the slope goes, so goes the velocity." A constant velocity motion is represented by a line of constant slope and a changing velocity by a line of changing slope. A positive velocity motion is represented by a line of positive slope and a negative velocity by a line of negative slope. A small velocity motion (slow object) is represented by a line with a small slope and a large velocity by a line with a large slope. In the end, by observing the slope, one can make conclusions about the velocity.

There are four very similar versions of this question. Each version provides a position-time graph of a five-stage motion and asks the learner to determine the stages in which the object is moving away from or towards the starting point. One of the versions is shown below.

Version 1
Five stages - labeled A, B, C, D, and E - of an object's motion are represented by the position-time graph below. During which stage(s) is the object moving away from its starting point?

This question is going to require a bit more thought. You must identify the stage(s) during which the object is moving towards or away from the starting position. First, you must know where the "starting position" is at. The starting position is the position along the vertical axis (y-axis) at a time of 0 seconds. That is, it is the position value that the line has where it touches the position axis (far left side of graph).

Once you know what "starting position" means, you can begin to answer the question. You are looking for any of the stages in which the object is (depending on the version of this question you get) moving towards or away from this position. This would correspond to a line that is getting closer to this vertical coordinate (for moving towards) or further away from this vertical coordinate (for moving away). That is, as you read the graph from left to right (from starting time to final time), you will be looking for a line whose position value is getting closer to or further away from this coordinate.

If you're still struggling with this question, it might help to imagine a horizontal line stretching across the screen from the starting position. You would be looking for any stage in which the line is approaching this horizontal line (for moving towards the starting position) or getting further from this horizontal line (for moving away from the starting position).

Try the links below to our Tutorial for more information about position-time graphs:

The Meaning of Shape for a p-t Graph

The Meaning of Slope for a p-t Graph

Determining the Slope on a p-t Graph