This module provides a brief tutorial on scale factors, ratios, and proportions that is designed to be accessible to blind students.
Table of contents
Preface
General
This module is part of a collection of modules designed to make physics
concepts accessible to blind students.
If you opened this page in the context of the book, a Table of Contents for
the book (or collection) should be available above and to the left of thisparagraph. Otherwise, click
here to open the book at the beginning.
This book is intended to supplement but not to replace the textbook in an
introductory high school or college physics course.
This module provides a brief tutorial on scale factors, ratios, and proportions that is
designed to be accessible to blind students.
Prerequisites
In addition to an Internet connection and a browser, you will need the
following tools (as a minimum) to work through the exercises in these modules:
 A graph board for plotting graphs and vector diagrams (
(External Link) ).
 A protractor for measuring angles (
(External Link) ).
 An audio screen reader that is compatible with your operating system,
such as the NonVisual Desktop Access program (NVDA), which is freelyavailable at
(External Link) .
 A refreshable Braille display capable of providing a line by line tactile output of information displayed on the computer monitor
(
(External Link) ).
 A device to create Braille labels. Will be used to label graphs
constructed on the graph board.
 The ability to create tactile graphics as described
here .
The minimum prerequisites for understanding the material in these modules
include:
 A good understanding of algebra.
 An understanding of the use of a graph board for plotting graphs and
vector diagrams (
(External Link) ).
 An understanding of the use of a protractor for measuring angles (
(External Link) ).
 A basic understanding of the use of sine, cosine, and tangent from
trigonometry (
(External Link) ).
 An introductory understanding of JavaScript programming (
(External Link) and
(External Link) ).
 An understanding of all of the material covered in the earlier modules
in this collection.
 An understanding of the creation and use of tactile graphics as
described
here .
Viewing tip
I recommend that you open another copy of this document in a separate
browser window and use the following links to easily find and view the figuresand listings while you are reading about them.

Figure 1 . Screen output for Listing #1.

Figure 2 . Screen output for Listing #2.

Figure 3 . Screen output for Listing #3.
Listings

Listing 1 . Exercise on scale factors

Listing 2 . Circumference is proportional to
radius.

Listing 3 . Area is proportional to radius squared.
Supplemental material
I recommend that you also study the other lessons in my extensive collection
of online programming tutorials. You will find a consolidated index at
www.DickBaldwin.com .