Skip to Content Go to sign in Skip to Primary Navigation Skip to Page Navigation Skip to Header Navigation Skip to Footer Navigation Toggle Accessibility Options or learn more about accessability

Physics Classroom is making strides to make our site accessible to everyone, and features many accessibility features.

Our site contains 6 navigation areas. The Primary, Secondary, and Page Level navigations have a screen reader version of their nav structure that allows using the left and right keys to navigate sibling navigation items, and up or down keys to navigate parent or child navigation items. The others can be navigated using tabs.

Within the main content, we leverage headers to provide in page or in tool navigation.

Although we are still rebuilding our content to leverage these tools, our images should have both short and verbose descriptions, the later describing in great detail the image for those who cannot see. Any formulas found within the images are often in the image figure below the image.

Equations and formulas are rendered using MathJax, which has both verbal, braille (including nemath braille), and keyboard navigation within them. Learn how to configure and leverage this for various screen readers on our Equation Navigation Page.

While not every area of Physics Classroom is usable purely from keyboard and screen reader, we are committed to continue work on making this possible. If you have questions or need additional help, please use this link to contact us .

Return to screen reader navigation

Chapter 2: 1D Kinematics - Lesson 5: Free Fall and the Acceleration of Gravity

Representing Free Fall by Graphs

  1. Introduction
  2. Acceleration of Gravity
  3. Representing Free Fall by Graphs
  4. How Fast? and How Far?
  5. The Big Misconception
Getting your Trinity Audio player ready...

Hold down the T key for 3 seconds to activate the audio accessibility mode, at which point you can click the K key to pause and resume audio. Useful for the Check Your Understanding and See Answers.

Early in Lesson 1 it was mentioned that there are a variety of means of describing the motion of objects. One such means of describing the motion of objects is through the use of graphs - position versus time and velocity vs. time graphs. In this part of Lesson 5, the motion of a free-falling motion will be represented using these two basic types of graphs.

 

Representing Free Fall by Position-Time Graphs

A position versus time graph for a free-falling object is shown below.

Observe that the line on the graph curves. As learned earlier, a curved line on a position versus time graph signifies an accelerated motion. Since a free-falling object is undergoing an acceleration (g = 9.8 m/s/s), it would be expected that its position-time graph would be curved. A further look at the position-time graph reveals that the object starts with a small velocity (slow) and finishes with a large velocity (fast). Since the slope of any position vs. time graph is the velocity of the object (as learned in Lesson 3), the small initial slope indicates a small initial velocity and the large final slope indicates a large final velocity. Finally, the negative slope of the line indicates a negative (i.e., downward) velocity.



 

Representing Free Fall by Velocity-Time Graphs

A velocity versus time graph for a free-falling object is shown below.

Observe that the line on the graph is a straight, diagonal line. As learned earlier, a diagonal line on a velocity versus time graph signifies an accelerated motion. Since a free-falling object is undergoing an acceleration (g = 9,8 m/s/s, downward), it would be expected that its velocity-time graph would be diagonal. A further look at the velocity-time graph reveals that the object starts with a zero velocity (as read from the graph) and finishes with a large, negative velocity; that is, the object is moving in the negative direction and speeding up. An object that is moving in the negative direction and speeding up is said to have a negative acceleration (if necessary, review the vector nature of acceleration). Since the slope of any velocity versus time graph is the acceleration of the object (as learned in Lesson 4), the constant, negative slope indicates a constant, negative acceleration. This analysis of the slope on the graph is consistent with the motion of a free-falling object - an object moving with a constant acceleration of 9.8 m/s/s in the downward direction.




 

Return to Screen Reader Navigation
Tired of Ads? Go Ad Free ($5/year))