This document discusses units of measurement and conversions in physics. It introduces the International System of Units (SI) which standardizes the basic units used to measure length, mass, time, temperature, electric current, luminous intensity, and amount of substance. Derived units are also discussed, along with common prefixes used to denote powers of ten when measuring larger or smaller quantities. Examples are provided for unit conversions between kilometers and meters, and kilometers per hour and meters per second. The document also differentiates between accuracy and precision in measurements.

1. BTU 1113 Physics Mohamad Rusydi
Fakulti Teknologi

2. At the end of this chapter, we will…
1.Understand the unit of measurement and its applications
2.Learn on how to use the prefixes
3.Solve the problems regarding the unit conversion

3. There are a few basic quantities in physics that are used for measurement. In 1960, it was standardize and is known as SI system units.
Quantities
SI Unit
Symbol
Length
Meter
m
Mass
Kilogram
kg
Time
Second
s
Temperature
Kelvin
K
Electric Current
Ampere
A
Luminous Intensity
Candela
Cd
Amount of substance
Mole
mol

4. Basic quantities can be derived and yield many other quantities and can be used for various measurement
Quantities
SI Unit
Symbol
Volume
cubic meter
m3
Density
kilograms per cubic meter
kg/m3
Speed
meter per second
m/s
Newton
kg m/ s2
N
Energy
Joule (kg m2/s2)
J
Pressure
Pascal (kg/(ms2)
Pa

5. Name
Symbol
Factor
tera-
T
1012
giga-
G
109
mega-
M
106
kilo-
k
103
hecto-
h
102
deka-
da
101
Prefixes are used to denote measurement in various power of ten. Some of normally used prefixes and their symbol are shown below;

6. Name
Symbol
Factor
deci-
d
10-1
centi-
c
10-2
milli-
m
10-3
micro-
μ
10-6
nano-
n
10-9
pico-
p
10-12
femto-
f
10-15

7. Name
Symbol
Application
Example
giga
G
PC memory
80 GB
mega
M
Electric power
200 MW
kilo
k
Distance
8 km
deci
d
Length
centi
c
Length
milli
m
Medicine
5 ml
micro
μ
Biology
Microb size -2 μm
nano
n
Astronomy
wv - 400 nm

8. M x 10n
M is the coefficient 1<M<10
10 is the base
n is the exponent or power of 10

9. 5.45E+6
-Normally used in a calculator display
-Also found in excel table
-Numbers less than 1 will have a negative exponent.
Ex: A millionth of a second is:
0.000001 sec can be denoted as
1x10-6 or 1.0E-6

10. Example 1: Convert 86 km to m:
Multiply the original measurement by a conversion factor.
86 km x 1,000 m = 86,000 m
1km

11. Example 2: Convert 75.00 km/h to m/s
75.00 km x 1000 m x 1 h___ = 20.83m/s
h 1 km 3600 s

12. 1.Convert 789 m to km
2.Convert 20 m/s to km/h

13. Accuracy
Precision

14. Accuracy
A measure of how close a measurement is to the true value of the quantity being measured.

15. Who is more accurate when measuring a book that has a true length of 17.0 cm?
Susan:
17.0 cm, 16.0 cm, 18.0 cm, 15.0 cm
Amy:
15.5 cm, 15.0 cm, 15.2 cm, 15.3 cm

16. Precision
A measure of how close a series of measurements are to one another. A measure of how exact a measurement is.

17. Who is more precise and accurate when measuring the same 17.0cm book?
Susan:
17.0cm, 16.0cm, 18.0cm, 15.0cm accurate
Amy:
15.5cm, 15.0cm, 15.2cm, 15.3cm precise

18. Accurate
Not Precise
Not Accurate
Precise
Accurate
Precise

19. The significant figures in a measurement include all of the digits that are known, plus one last digit that is estimated.

21. When the decimal is present, start counting from the left.
When the decimal is absent, start counting from the right.
Zeroes encountered before a non zero digit do not count.

22. 100 10302.00
0.001
10302 1.0302x104

23. Express the result with the same number of decimal places as the number in the operation with the least decimal places.
Ex: 2.33 cm
+ 3.0 cm
5.3 cm
(Result is rounded to one decimal place)

24. Express the answer with the same sig figs as the factor with the least sig figs.
Ex: 3.22 cm
x 2.0 cm
6.4 cm2 (Result is rounded to two sig figs)

25. Counting numbers have infinite sig figs.
Ex: 3 apples

26. At the end of this chapter, you should be able to…
1.Understand the unit of measurement and its applications
2.Learn on how to use the prefixes
3.Solve the problems regarding the unit conversion