Lesson 4: Units (prefixes), and Measurement and Safety
Video Lesson
Lesson Objective
Dear Learners,
At the end of this section, you should be able to:
- List different instruments used to measure physical quantities such as length, area, volume, mass, and time in their local area;
- List modern length, mass and time measuring devices.
- Measure length, mass and time using different units.
Brainstorming Question
What measuring devices are used to measure volume, mass and length in your local area?
key terms and concepts
- Prefix
- Time
- Length
- Mass
Prefix is a letter or a syllable which is written directly before a unit name with no space.
Time is a basic physical quantity. It describes the duration between the beginning and end of an event.
Length is the fundamental physical quantity that describes the distance between two points.
Mass is a basic physical quantity. It is defined as the amount of matter contained in a body.
Prefixes
Prefix is a letter or a syllable which is written directly before a unit name with no space. Here is a table listing some common prefixes used in the International System of Units (SI) along with their symbols and factors:
| Prefix | Symbol | Factor | Scientific Notation |
|---|---|---|---|
| Tera | T | 1,000,000,000,000 | $10^{12}$ |
| Giga | G | 1,000,000,000 | $10^{9}$ |
| Mega | M | 1,000,000 | $10^{6}$ |
| Kilo | k | 1,000 | $10^{3}$ |
| Hecto | h | 100 | $10^{2}$ |
| Deca | da | 10 | $10^{1}$ |
| (Base Unit) | (none) | 1 | $10^{0}$ |
| Deci | d | 0.1 | $10^{-1}$ |
| Centi | c | 0.01 | $10^{-2}$ |
| Milli | m | 0.001 | $10^{-3}$ |
| Micro | μ | 0.000001 | $10^{-6}$ |
| Nano | n | 0.000000001 | $10^{-9}$ |
| Pico | p | 0.000000000001 | $10^{-12}$ |
Measurement
In physics, measurement is the process of quantitatively comparing an unknown quantity with a standard unit of the same kind. It involves using tools and techniques to determine the value of a physical quantity, such as length, mass, time, temperature, or electric current. The measurement process has three key elements:
1. Physical Quantity
2. Unit
3. Measurement Instrument
Measuring Length
Length is the fundamental physical quantity that describes the distance between two points. The SI unit of length is meter(m). The instrument used to measure length is shown below.
Meter Tape
Micro meter
Vernier caliper
Measuring Mass
Mass is a basic physical quantity. It is defined as the amount of matter contained in a body. The S.I unit of mass is the kilogram(kg). The instrument used to measure mass is shown below.
Beam balance.
Digital balance.
Analog balance.
Measuring Time
Time is a basic physical quantity. It describes the duration between the beginning and end of an event. The S.I unit of time is second(s). The instrument used to measure time is shown below.
Digital watch
Clock
Stop watch
Laboratory Safety rules
Students should follow the general laboratory safety guidelines so that working in the physics laboratory can be a safe and enjoyable process of discovery. For example, some of these safety rules are:
- Always wear a lab safety goggle.
- Avoid wearing baggy clothing, bulky jewelry, dangling bracelets, open-toed shoes or sandals.
- NEVER work alone in the laboratory.