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1-D Kinematics - Lesson 4

Describing Motion with Velocity vs. Time Graphs

Student Extras

PhET Simulation: The Moving Man More about this relation

Explore the relationship between motion graphs and motion with PHET's The Moving Man simulation.

Apply the Brakes More about this relation

Explore the difference between constant speed and accelerated motion with the Apply the Brakes simulation.

Flickr Physics

Visit The Physics Classroom's Flickr Galleries and take a visual overview of 1D Kinematics.

Shockwave Studios

Think you get the idea? Try the Graph That Motion activity from the Shockwave Studios.

Teacher's Guide

PhET Simulation: The Moving Man More about this relation

Explore the relationship between graphs and motion with The Moving Man simulation from PHET.

Apply the Brakes More about this relation

This Apply the Brakes simulation provides multiple representations of constant speed and accelerated motion.

Graph Matching Motion Model More about this relation

This EJS simulation from Open Source Physics (OSP) contrasts the graphs for constant speed and accelerated motion.

Shockwave Studios

Graph That Motion from the Shockwave Studios is an excellent accompanying activity to this page.

The Laboratory

Looking for a lab that coordinates with this page? Try the Velocity-Time Graphs Lab at The Laboratory. Requires motion detectors.

Curriculum Corner

Learning requires action. Give your students this sense-making activity from The Curriculum Corner.

Treasures from TPF

Need ideas? Explore The Physics Front's treasure box of catalogued resources on kinematic graphing.

Relating the Shape to the Motion

As discussed in a previous part of Lesson 4, the shape of a velocity vs. time graph reveals pertinent information about an object's acceleration. For example, if the acceleration is zero, then the velocity-time graph is a horizontal line - having a slope of zero. If the acceleration is positive, then the line is an upward sloping line - having a positive slope. If the acceleration is negative, then the velocity-time graph is a downward sloping line - having a negative slope. If the acceleration is great, then the line slopes up steeply - having a large slope. The shape of the line on the graph (horizontal, sloped, steeply sloped, mildly sloped, etc.) is descriptive of the object's motion. This principle can be extended to any motion conceivable. In this part of the lesson, we will examine how the principle applies to a variety of types of motion. In each diagram below, a short verbal description of a motion is given (e.g., "constant, rightward velocity") and an accompanying ticker tape diagram is shown. Finally, the corresponding velocity-time graph is sketched and an explanation is given. Near the end of this page, a few practice problems are given.









Investigate!

The widget below plots the velocity-time plot for an accelerating object. Simply enter the acceleration value, the intial velocity, and the time over which the motion occurs. The widget then plots the line with position on the vertical axis and time on the horizontal axis.

Try experimenting with different signs for velocity and acceleration. For instance, try a positive initial velocity and a positive acceleration. Then, contrast that with a positive initial velocity and a negative acceleration.





Check Your Understanding

Describe the motion depicted by the following velocity-time graphs. In your descriptions, make reference to the direction of motion (+ or - direction), the velocity and acceleration and any changes in speed (speeding up or slowing down) during the various time intervals (e.g., intervals A, B, and C). When finished, click the button to see the answers.