Kinematic Graphing - Mission KG3 Detailed Help

The motions of five objects - A, B, C, D, and E - are represented by lines on a position-time graph. Write the letter(s) for any object that is slowing down (getting slower). List all that apply.

Position-Time Graphs:
Position versus time graphs represent changes that occur in an object's position with respect to time. The slope of the line is the velocity (change in position divided by the change in time) of the object.

The slope of the line represents the velocity of the object. The velocity is the speed with a direction. So the magnitude of the slope is the speed of the object. An object that is slowing down is an object with a decreasing speed. Thus, this question is asking you to identify the lines on the graph that have a decreasing slope. So inspect each line looking for any that change their slope from a large slope (steep) to a small slope (flatter).

Many students become confused by the phrase slowing down. Because of the presence of down in the phrase, they begin to restrict their answers to those lines that are sloping down. But don't be fooled! Sloping down does not mean slowing down. A line that simply slopes down is a line with a negative slope and thus a negative velocity. An object that slows down is an object with a decreasing speed. An object can move in the positive direction (and have a line sloping upward) and still be slowing down (if the line is getting flatter).


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