Introduction to the Model

Description and Assumptions

This model is applicable to a single point particle moving with constant velocity, which implies that it is subject to no net force (zero acceleration). Equivalently, the model applies to an object moving in one-dimension whose position versus time graph is linear. It is a subclass of the One-Dimensional Motion with Constant Acceleration model defined by the constraint a = 0.

Learning Objectives

Students will be assumed to understand this model who can:

• Describe the difference between distance and displacement.
• Define average velocity and average speed.
• Describe the features of a motion diagram that exhibits motion with constant velocity.
• Relate displacement, time and velocity.
• Find velocity from the slope of a position versus time graph.
• Describe the properties of the position versus time graph given the velocity and the initial position for a trip made at constant velocity.
• Mathematically determine when two objects moving with constant velocity will meet by constructing and solving a system of equations.
• Graphically determine when two objects moving with constant velocity will meet.

S.I.M. Structure of the Model

Compatible Systems

A single point particle (or a system treated as a point particle with position specified by the center of mass).

Relevant Interactions

In order for the velocity to be constant, the system must be subject to no net force.

Law of Change

Mathematical Representation

\begin{large}\[x(t) =  x_{i} + v (t - t_{i})\]\end{large}

Diagrammatic Representations

• motion diagram
• position versus time graph
• velocity versus time graph

Relevant Examples

Examples Involving Purely One-Dimensional Motion

Examples Involving Determining when Two Objects Meet

Examples Involving Projectile Motion

All Examples Using This Model