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0. Fundamental Concepts
Physics is forever-changing science, requires students to have a solid knowledge of mathematics, including algebra, chemistry, and biology. This subject is very useful in the real world, as this explains the world around us. A lot of formulas are used, including F=ma, to represent many of the Earth's simple mechanisms. Simple, child-like questions such as "How will I catch the ball?" and "How far should I push this punching bag?" are physics-related questions. You have been dealing with physics since you were born!
In 1971, the 14th General Conference on Weights and Measures picked seven quantities as base quantities, thereby forming the basis of the International System of Units, abbreviated SI from its French name and popularly known as the metric system. There are seven base quantities used in the International System of Units. The seven base quantities and their corresponding units are:
- time (second)
- length (metre)
- mass (kilogram)
- electric current (ampere)
- thermodynamic temperature (kelvin)
- amount of substance (mole)
- luminous intensity (candela)
These base quantities are assumed to be independent of one another. In other words, no base quantity needs to be defined in terms of any other base quantity (or quantities). Note however that although the base quantities themselves are considered to be independent, their respective base units are in some cases dependent on one another. The metre, for example, is defined as the length of the path travelled by light in a vacuum in a time interval of 1/299 792 458 of a second.
Suppose that you work out a problem in which each value consists of two digits. Those digits are called significant figures and they set the number of digits that you can use in reporting your final answer. With data given in two significant figures, your final answer should have only two significant figures. However, depending on the mode setting of your calculator, many more digits might be displayed. Those extra digits are meaningless.
When a number such as 3.15 or 3.15 × 103 is provided in a problem, the numer of significant figures is apparent, but how about the number 3000? Is it known to only one significant figure (3 × 103)? Or is it known to as many as four significant figures (3.000 × 103)? We assume that all the zeros in such given numbers as 3000 are significant, but you had better not make that assumption elsewhere, like in case of 0.0003. Here we have only one significant figures.
Don’t confuse significant figures with decimal places. Consider the lengths 35.6 mm, 3.56 m, and 0.00356 m. They all have three significant figures but they have one, two, and five decimal places, respectively.
To express the very large and very small quantities we often run into in physics, we use scientific notation, which employs powers of 10. For example, we can write 0.00015 or 1.5 × 10-4. Sometimes you can find computational like notation with E or e. This example will look like this 1.5E-4 or 1.5e-5.
Additionaly a metric prefix is a unit prefix that precedes a basic unit of measure to indicate a multiple or fraction of the unit. Each prefix has a unique symbol that is prepended to the unit symbol. The prefix kilo-, for example, may be added to gram to indicate multiplication by one thousand: one kilogram is equal to one thousand grams. The prefix milli-, likewise, may be added to metre to indicate division by one thousand; one millimetre is equal to one thousandth of a metre. The SI prefixes are metric prefixes that were standardized for use in the International System of Units (see table below).
| Name | Symbol | Base 10 | Decimal |
|---|---|---|---|
| yotta | Y | 1024 | 1000000000000000000000000 |
| zetta | Z | 1021 | 1000000000000000000000 |
| exa | E | 1018 | 1000000000000000000 |
| peta | P | 1015 | 1000000000000000 |
| tera | T | 1012 | 1000000000000 |
| giga | G | 109 | 1000000000 |
| mega | M | 106 | 1000000 |
| kilo | k | 103 | 1000 |
| hecto | h | 102 | 100 |
| deca | da | 101 | 10 |
| - | 1 | one | – |
| deci | d | 10−1 | 0.1 |
| centi | c | 10−2 | 0.01 |
| milli | m | 10−3 | 0.001 |
| micro | μ | 10−6 | 0.000001 |
| nano | n | 10−9 | 0.000000001 |
| pico | p | 10−12 | 0.000000000001 |
| femto | f | 10−15 | 0.000000000000001 |
| atto | a | 10−18 | 0.000000000000000001 |
| zepto | z | 10−21 | 0.000000000000000000001 |
| yocto | y | 10−24 | 0.000000000000000000000001 |