1. SI Units Of Measurements
Measurement make sense only, if it has both number and Unit.
ex. 6 inches, 12 dollars.
Some examples of units are inches, feet, pounds, degree Fahrenheit.
A set of measuring units called SI, or the Inter national System of Units.
SI is a revised version of metric system, which was originally developed in France in 1791.
The abbreviation stands for French name System International d’Unites.

2. Base Units and Derived Units
SI has 7 metric units known as base units,
which are as follows.
Quantity
Unit
Symbol
Length
meter m
Mass
kilogram kg
Temperature
Kelvin K
Time
second s
Amount of substance
mole
mol
Electric current
ampere A
Luminous Intensity
candela cd

3. Derived Units Additional SI Units, which are made from a combination of base units ex. Area, Volume, Density etc.
Quantity
Unit
Symbol
Area
Square meter m²
Volume
Cubic meter m³
Density
Kg per cubic meter
Kg/m³
Frequency
hertz Hz
wavelength
meter m
Velocity
Speed
m/s direction
m/s v v̅
Acceleration
Meters per second per second
m/s² or m/s/s

4. Quantity
Unit
Symbol
Power
J /s W
Force
Kg.m/s² N
Momentum
Kilogram meter per s
Kg.m/s
Work
Joule J
Energy

5. 1) Length a. The distance from one point to another point. b
1) Length a . The distance from one point to another point b. Base unit is the meter (m) c. Centimeter or inch ruler is used to measure length c
2). Mass
a. The amount of matter in a substance.
b. Base unit - kilogram (kg).
The tool used is a triple beam balance. (Grams g)
3). Temperature
a. The amount of kinetic energy a substance has.
b. SI unit is the Kelvin (K).

6. Volume a. The amount of space a substance occupies.
For regular shaped solids use the equations
L X W X H.
but for an irregular shaped solid we use a graduated cylinder and measure how much water is displaced.
( m³ or L )
b. Base unit is the liter (L).
1 L = 1 m³

7. Temperature Definition – A measure of the heat of an object
Thermometer – A device that measures temperature,
usually with mercury.
There are three temperature scales .
1) Fahrenheit scale. 2) Celsius scale 3) SI Unit scale or Kelvin scale.
Some baseline temperatures in the three different temperature scales:
Temperature
Celsius
Fahrenheit
Kelvin
Symbol °C °F K
Melting point of ice 32
273
Boiling point of water
100
212
373
-273
-460

8. International system of units (SI)
Used in many countries to have a uniform scale of measurement.
1. Based on multiples of Common metric prefixes

9. Conversions: Units based on 10

10. Conversions
C/100 = (F-32)/180 Celsius = 5/9 X (Fahrenheit -32) Fahrenheit =( 9/5 x Celsius) + 32 Kelvin = Celsius + 273

11. Units of distance in space
An “Astronomical Unit” (AU) is a convenient way to measure distances in the solar system.
It is the average distance from the earth to the sun, about 150 million kilometers (1.5 X 108 km or 93 million miles)
1 mile = 1.6 km.
One light year is equal to the distance that light travels through space in one year (9.46 × 1012 km)

12. Accuracy & Precision in Measurement

13. Precision
Depends on the How finely tuned your measurements are or how close they can be to each other.
It depends on measuring tool.
Determined by more number of significant digits.
If the analog clock is showing 5 minutes and the digital clock is showing 5 minutes 15 seconds, the digital clock is showing more precise measurements.

14. Accuracy: How close you are to the actual value
Depends on the person measuring
Even if the digital clock is more precise by showing 5 minutes 15 seconds but if it is running slow. Although the clock is precise to the nearest seconds, the time displayed is not accurate.