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Home Concept Builders 1D Kinematics Dots and Graphs Help Help 1

Dots and Graphs - Questions 1 Help

The slope of a position-time graph provides insight about the velocity of the object. By carefully interpreting the slope of the line and how it changes over time, one can determine the manner in which the object is moving - constant speed, speeding up, slowing down, and the direction of motion.

There are four similar versions of this question. Each includes three horizontal lines and three diagonal lines on a position-time graph. Here is one of the versions:
 

Version 1:

Consider the dot diagrams for Objects A, B, and C. The arrow represents the direction of motion. Match the motion of Objects A, B, and C to one of the lines on the graph. Numbers can be used only one time.
 

You have to match the motions of A, B, and C to one of the six lines on the position-time graph. That's going to require some good thinking and decision-making. The following should help:

Positive vs. Negative Velocity: For each object, you need to decide whether the velocity is positive or negative. Look at the arrow on the dot diagram; it indicates the direction that the object is moving. Typically a leftward motion is considered a negative velocity and a rightward motion is a positive velocity. A positive velocity is represented by a line with positive slope and a negative velocity by a line with negative slope.

Fast vs. Slow: The three objects have different speeds. The amoiunt of space (distance) between adjacent dots reveals the speed. A large spacing corresponds to an object with high speed. Match this object to the line with the greatest slope since the steepest line - whether upward sloped or downward sloped - corresponds to the fastest object. In a similar manner, match the object with the smallest speed to the line with the smallest slope.

The following pages from The Physics Classroom Tutorial may provide additional background information and help with the topics in this Concept Builder:

Position-Time Graphs: Meaning of Shape

Dot Diagrams

Concept Builder Teacher Notes Directions