When one quantity changes at a constant rate with respect to another, we say they are linearly related. Mathematically, we describe this relationship by defining a linear equation. In real-world applications, some quantities are linearly related and can be represented by using a straight-line graph.

In this activity, you will create straight-line, or constant-speed, position versus time plots using a Motion Detector, and then develop linear equations to describe these plots mathematically.


  • Record distance versus time data for a person walking at a uniform rate.
  • Analyze the data to extract slope and intercept information.
  • Interpret the slope and intercept information for physical meaning.