The Passing Lane

A GIF Animation

Observe the two cars below. The blue car starts "ahead of" the red car (which actually starts "off the screen"). Since the red car is moving faster, it eventually catches up with and passes the blue car. Observe the velocity-time graphs for these two cars. Each car's motion is represented by a horizontal line, indicating a constant velocity. Observe that even though the cars pass each other, the lines on the velocity-time graphs do not intersect. Since the cars never have the same velocity, the lines on the velocity-time graph never cross. The lines would intersect for a position vs. time graph; the fact that the red car passes the blue car means that there is an instant in which they occupy the same position. The two cars have the same position at seven seconds; yet they never have the same velocity at any instant in time.

Animation of two cars with v-t Graphs

For more information on physical descriptions of motion, visit The Physics Classroom. Specific information is available there on the following topics:

Other animations can be seen at the Multimedia Physics Studios. Other useful resources regarding the physics of motion is available through the Glenbrook South Physics Home Page.

This page was created by Tom Henderson of Glenbrook South High School.

Comments and suggestions can be sent by e-mail to Tom Henderson.

This page last updated on 2/28/97.