$35.49
Author: Holzner
Brand: For Dummies
Edition: 2
Number Of Pages: 334
Details: Excerpt. © Reprinted by permission. All rights reserved.
Physics I Workbook For Dummies
By Steven Holzner John Wiley & SonsCopyright © 2014 John Wiley & Sons, Ltd
All rights reserved.
ISBN: 978-1-118-82577-8
CHAPTER 1
Reviewing Physics Basics
In This Chapter
* Laying down measurements
* Simplifying with scientific notation
* Practicing conversions
* Drawing on algebra and trigonometry
This chapter gets the ball rolling by discussing some fundamental physics measurements. At its root, physics is all about making measurements (and using those measurements as the basis of predictions), so it’s the perfect place to start! I also walk you through the process of converting measurements from one unit to another, and I show you how to apply math skills to physics problems.
Measuring the Universe
A great deal of physics has to do with making measurements — that’s the way all physics gets started. For that reason, physics uses a number of measurement systems, such as the CGS (centimeter-gram-second) system and the MKS (meter-kilogram-second) system. You also use the standard English system of inches and feet and so on — that’s the FPI (foot-pound-inch) system.
REMEMBER
In physics, most measurements have units, such as meters or seconds. For example, when you measure how far and how fast a hockey puck slid, you need to measure both the distance in centimeters and the time in seconds.
For reference, Table 1-1 gives you the primary units of measurement in the MKS system.
These are the measuring sticks that will become familiar to you as you solve problems and triumph over the math in this workbook. Also for reference, Table 1-2 shows the primary units of measurement (and their abbreviations) in the CGS system. (Don’t bother memorizing the ones you’re not familiar with now; you can come back to them later as needed.)
EXAMPLE
Q. You’re told to measure the length of a race car track using the MKS system. What unit(s) will your measurement be in?
A. The correct answer is meters. The unit of length in the MKS system is the meter.
1. You’re told to measure the mass of a marble using the CGS system. What unit(s) will your measurement be in?
Solve It
2. You’re asked to measure the time it takes the moon to circle the Earth using the MKS system. What will your measurement’s units be?
Solve It
3. You need to measure the force a tire exerts on the road as it’s moving using the MKS system. What are the units of your answer?
Solve It
4. You’re asked to measure the amount of energy released by a firecracker when it explodes using the CGS system. What are the units of your answer?
Solve It
Putting Scientific Notation to Work
Physics deals with some very large and very small numbers. To work with such numbers, you use scientific notation. Scientific notation is expressed as a number multiplied by a power of 10.
For example, suppose you’re measuring the mass of an electron in the MKS system. You put an electron on a scale (in practice, electrons are too small to measure on a scale — you have to see how they react to the pull of magnetic or electrostatic forces to measure their mass), and you measure the following:
0.00000000000000000000000000000091 kg
What the heck is that? That’s a lot of zeros, and it makes this number very unwieldy to work with. Fortunately, you know all about scientific notation, so you can convert the number into the following:
9.1 × 10-31 kg
That is, 9.1 multiplied by a power of 10, 10-31. Scientific notation works by extracting the power of 10 and putting it on the side, where it’s handy. You convert a number to scientific notation by counting the number of places you have to move the decimal point to get the first digit in front of that decimal point. For example, 0.050 is 5.0 × 10-2 because you move the decimal point two places to the right to get 5.0. Similarly, 500 is 5.0 × 102 because you move the decimal point two places to the left to get 5.0.
Check out this practice question about scientific notation:
EXAMPLE
Q. What
Release Date: 21-03-2014
Package Dimensions: 22x254x760