Meet the Units

Units in General

Whenever we are discussing applied mathematics (this includes the physical sciences, we have to use units. Any work or anwer without units is incorrect. A speed of 140 may be a high

speed if thinking in terms of kilometers per hours, however it is an enormous speed when thinking in terms of miles per hours and it is even a more enormous speed when using the unit

system meters per second.

Si Units

A very good resource for learning about units of measure as well as universal constants is the web-site of the National Institute of Standards and Technology NIST

http://physics.nst.gov/Units/ The International System of Units (abbreviated Sl from the French Systeme international unite uses the decimal system and several base units. There

are many units that we use in every day life that are not Si units, and we need to be able to convert them correctly (we will discuss this and do some problems when we get to dimensional

analysis)

Q1. Answer all parts of this question in your own words.

1. What is a base unit?

2. What is the name and symbol of the base unit for:

o

length

o

mass

o time

o electric current

o thermodynamic temperature

o amount of substance

3. Use the following example, do the same for the prefixes centi, milli, and

kilo.

o "The prefix deci means one-tenth. There are 10 dm (decimeters)

in 1 m (meter). There are 10 dg (decigrams) in 1 gram."

4. What is a derived unit?

5. What is the name and symbol for the derived unit for:

o area

o (mass) density