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Common Knowledge

Good students in grade 8 should know almost all of the common knowledge given on this page. Some students, used to seeing only "Bill Nye" videos, may not be familiar with the actual units involved with common measurements. What follows is a good review of these units, followed by a quick review of their use in the real world. All Jr. High and High School Students shold know the following relationships between different units.

Everyone should be familier with a meter stick. It is a meter in length. Saying it is about 39.37 inches long or that 1 inch = 2.54 cm does not give the familiarity of holding an actual meter stick. For the same reason, holding a kilogram mass and getting the feel of moving it around is better then saying it is approximately the same as a 2.20462 lb mass. Looking at a clock an actually counting the seconds of time is better then any estimate.

Speaking of seconds, note that there are 60 seconds in a minute, 60 minutes in an hour, and 24 hours in a solar day. A solar day is the mean time it takes for a day-night cycle. There are 365 days, 5 hours, 48 minutes and 46 seconds in a year [or about 365.2422 days] which is the time it takes the Earth to go around the Sun once. The time it takes for the Earth to revolve on its axis once in relation to the starts is a sidereal day which is about 23 hours and 56 minutes in length.

The length of a year is about 365 days 5 hours 48 minutes and 46 seconds or about 365.2422 days.

The average time from Full Moon to Full Moon is about 29.53 days.

There are 5280 feet in a mile.

There are 8 pints in a gallon.

There are 16 fluid ounces in a pint.

"A pint is a pound the world around." (A pint of cold water)

There are 16 avoirdupois ounces per avoirdupois pound (453.59. g) (Avoirdupois is the standard pound we use.)

There are 12 troy ounces per troy pound. (373.24 g) (gold, silver, etc.)

A decimeter is a tenth of a meter. [about 3 15/16 inches]

A cubic decimeter is a liter.

A liter of cold water [4C] has a mass very close to a kilogram.

In the Southern United States, a kilogram has a weight close to 9.8 newtons (N).

That means if you drop a heavy object, it will follow A = F/M = 9.8 N / 1.0 kg = 9.8 m/s2. In other words, it will accelerate at the rate of 9.8 meters per second every second which is about 22 mph every second.

The work (energy) required to lift that kilogram one meter is 9.8 joules since energy is the product of force and distance.

The power required to lift that kilogram one meter in one second is 9.8 watts since power is the product of force and speed. One horsepower is 746 watts or 746 N-m/s or 375 lb-mph.

A centimeter (cm) is one hundreth of a meter, a millimeter (mm) is one thousandth of a meter, a micrometer (m) is one millionth of a meter and a nanometer (nm) is one billionth of a meter.

A kilometer (km) is a thousand meters, a megameter (Mm) is a million meters, and a gigameter (Gm) is one billion meters. Distance from the Equater to the North Pole through Paris is about 10 megameters (Mm). Do not confuse Mm with mm.

A kilogram is a thousand grams, but a million grams is a metric tonne. Also note that the U.S. medical profession uses (mcg) instead of (g) for microgram.

EMF (E) in volts is the product of current (I) in amps and resistance (R) in ohms. E=IR

Power (P) in watts is also the product of EMF (E) in volts and current (I) in amps. P=IE

Energy in joules (j) is also the product of power in watts (W) and time in seconds (s). Energy in kWh is the product of power in kilowatts (kW) and time in hours (h). 1 kWh = 3.6 Mj

Young humans with good hearing can hear sounds from about 20 Hertz (Hz) to 20 kiloHertz (kHz). Required loudness depends on a persons hearing at each frequency.

Most humans have three kinds of cones in their eye that allows them to see the primary colors of red, green & blue. For that reason, these are the colors of the three phosphers or LEDs in a color TV or computer monitor.

Water freezes at sea level at 0C (centigrade) which is the same as 32F (Fahrenheit).

Water boils at sea level (standard atomospheric pressure) at 100C (centigrade) which is the same as 212F (Fahrenheit).

Standard atmospheric pressure at sea level is 101.325 kilopascals (kPa) or about 14.7 psi (pounds per square inch). This is enough pressure to support of column of mercury about 760 mm high, or about 30 inches. This is also enough pressure to support a column of water about 33 feet high. (Standard Pressure, on the other hand, is defined as 100 kPa,)

One BTU (British Thermal Unit) will raise 1 lb of water about 1F, about 1054.8 J (joules).

One gram calorie will raise 1 g of water about 1C, about 4.181 J. (A large calorie is a kilogram calorie.)

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