0.22 Phy1200: energy -- power

Table of contents

• Preface
  • General
  • Prerequisites
  • Supplemental material
• General background information
• Sample calculations
• Do the calculations
• Resources
• Miscellaneous

Preface

General

This module is part of a book (or collection) designed to make physics concepts accessible to blind students. The collection is intended to supplement but not to replace thetextbook in an introductory course in high school or college physics.

This module explains power in a format that is 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 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.

Supplemental material

I recommend that you also study the other lessons in my extensive collection of online programming tutorials. Youwill find a consolidated index at www.DickBaldwin.com .

General background information

What is work?

You learned in an earlier module that work occurs when a force causes a mass to be displaced by some distance. You learned that the equation for the quantity of work done is equal to

W = (f*newton)*(d*meter) = f*d*N*m

You also learned that work is measured in joules, where one joule is equal to one newton multiplied by one meter.

1 joule = 1 N * 1 m, or

1 joule = (1 kg * m/s^2) * m, or

1 joule = 1 kg*m^2/s^2

Paste the right-hand expression into the Google search box and press Enter just to be sure.

What about time?

Note that the equation for work says nothing about time. The same amount of work is done if it takes one second or one month for the object to which theforce is applied to move by the same distance.

That doesn't sound right!

This goes against our normal concept of work. If Joe spreads one cubic yard of topsoil on the lawn in one hour and Bill requires three hours to do the samejob, we might say that Joe is working harder than Bill.