1.
Dimensions vs Units:
·
A dimensions is a measurable extent. Height, length
·
A unit lets us to quantify a dimension.
·
Length is dimension, there are many units of length such as miles
and feet.
2. SI Prefixes:
·
Based on multiples of 10.
·
We avoid scientific notation or long strings of zeros.
·
Instead of: 198,000 We say: 198 Kilometers
3. The 7 fundamental dimensions & base units:
·
Dimension: Length Symbol: L
·
Dimension: Mass Symbol: M
·
Dimension: Time Symbol: T
·
Dimension: Amount of Substance Symbol: N
·
Dimension: Light intensity Symbol: J
·
Dimension: Electric Current Symbol: I
·
Unit: Kilogram Symbol: kg
·
Unit: Meter Symbol: M
·
Unit: Second Symbol: s
·
Unit: Kelvin Symbol: K
·
Unit: Mole Symbol: mol
·
Unit: Candela Symbol: cd
·
Unit: Ampere Symbol: A
4. Official SI rules:
·
If the unit abbreviation is a capital letter, it’s named after a
person.
·
Symbols of units are not plural (cm, not cms.)
·
You do not put a period after the symbol unless at the end of a
sentence.
·
Symbols are written like (m, k, L) not (m, k, l)
·
One space separates the number and symbol.
·
Spaces or commas may be used to group digits by threes.
·
Symbols with multiple units are joined with a space or interpunct.
·
Do not combine prefixes to form compound prefixes. Correct;
picojoules (pJ) Incorrect; kiloMegaseconds (kMs)
5.
Difference in SI, AES and
USCS. What are they? Which do you prefer? Why?:
·
SI: System International (meters, kilograms, seconds, kelvin,
celcius)
·
AES: American Engineering System (feet, pounds, seconds, Fahrenheit,
rankine)
·
USCS: United States Customary System (feet, slug, second, Fahrenheit,
rankine)
·
I prefer to use AES and USCS only because I am used to the units
and I have used them before.
6. Unit Conversion Procedure:
·
This was a difficult topic to understand. However, the procedure
is as follows.
·
Write the value and unit to be converted.
·
Write the conversion formula between the given unit and the
desired unit.
·
Make a fraction, equal to 1, of the conversion formula in Step 2,
such that the original unit in step 1 is located either in the denominator or
in the numerator.
·
Multiply the term from step 1 by the fraction developed in step 3.
·
Cancel units, perform mathematical calculations, and express the
answer in reasonable terms.
7.
Unit Conversion Procedure
involving multiple steps:
·
Refer to table 7-4 to 7-8 in Thinking like an Engineer. Page 161
