# The Science of Physics Section 1-2 Holt

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The Science of Physics Section 1-2 Holt
Measurements in Experiments

“Weights and measures may be ranked among the necessaries of life to every individual of human society. They enter into the economical arrangements and daily concerns of every family. They are necessary to every occupation of human industry; to the distribution and security of every species of property; to every transaction of trade and commerce; to the labors of the husbandman; to the ingenuity of the artificer; to the studies of the philosopher; to the researches of the antiquarian; to the navigation of the mariner, and the marches of the soldier; to all the exchanges of peace, and all the operations of war. The knowledge of them, as in established use, is among the first elements of education, and is often learned by those who learn nothing else, not even to read and write. This knowledge is riveted in the memory by the habitual application of it to the employments of men throughout life.” JOHN QUINCY ADAMS - Report to the Congress, 1821

Measurements Measurements play a BIG role in science.
Measurements are taken so comparisons can be made. Measurements are used to communicate results.

Measurement Measurements include a number and unit of measure. Examples? 10 inches pounds Units used in Science: Systeme International d’Unites or SI units Modern version of metric system

SI Units Symbol Unit Abbreviation Length meter m Mass kilogram kg Time
second s Electrical current ampere A Thermodynamic temperature Kelvin K Luminous intensity candela cd Amount of substance mole mol

Derived Units Derived units are combinations of other units. Examples:

Derived Units Derived units are combinations of other units. Examples:
Speed: miles per hour or meters per second (m/s) Force: kilograms x meters / seconds2

Meter Old Standard: 1/10,000,000 distance from equator to North Pole
Current Standard: Distance light travels in a vacuum in seconds

Kilogram Old Standard: mass of 0.001 cubic meters of water
Current Standard: mass of a specific platinum-iridium alloy cylinder

Second Old Standard: 0.00001574 average solar days
Current standard: 9,192,631,770 times the period of a radio wave emitted from a cesium-133 atom https://www.youtube.com/watch?v=MI9oOHrVI5M

Length in Metric Units Centimeter-width of fingernail on your pinky
Millimeter- width of a penny Meter- distance from floor to door knob

Mass in Metric Units Gram- 5 grams = mass of a nickel
Kilogram (1000 grams) --- about 2.2 cans of beans

Volume in Metric Units 12 oz pop = 355 milliters (mL)

Metric Units Prefix + base unit = metric unit
Prefixes are added to base units to show how much bigger or smaller the unit is. The metric system is based on powers of 10.

Metric Units Prefixes indicating larger quantities than base unit:
Kilo times bigger Hecto—100 times bigger Deca---10 times bigger Examples: Kilogram (kg) —1000 grams (g) Decaliter (da) – 10 liters (L)

Metric Units Prefixes indicating smaller quantities than base unit:
deci---10 times smaller centi—100 times smaller milli times smaller Examples: centimeter (cm) —0.01 meters (m) milliliter (mL) – liters (L)

Many more prefixes See Table 1-3 for more prefixes used in metric system. n = µ = M = G =

Converting Metric Units
Unit conversions in metric system much easier than in English system. Refer to handout. See which way to move decimal. 300 meters (m) = ________ centimeters (cm) 400 kilograms (km) = ________ grams (g) 7200 milliliters (mL) = _______ liters (L) You need to memorize prefixes from kilo to milli and be able to make these conversions without chart.

Converting Metric Units
Unit conversions in metric system much easier than in English system. Refer to handout. See which way to move decimal. 300 meters (m) = 30,000 centimeters (cm) 400 kilograms (km) = 400,000 grams (g) 7200 milliliters (mL) = 7.2 liters (L) You need to memorize prefixes from kilo to milli and be able to make these conversions without chart.

Powers of 10 Numbers often expressed as powers of 10 when they are very small or very large = 3 x 10-5 = 6.1 x 109

Scientific Notation Scientific Notation: Examples: 3.2 x 10-3 9 x 107
First number is and Taken times 10 to some power Examples: 3.2 x x 107

Homework-Refer to syllabus
Quiz—You will be having a quiz soon on being able to visualize size of metric quantities.