Measurement & Uncertainty
FUNDAMENTAL QUANTITY
• Mass
SI SYSTEM
kilogram (kg)
ENGLISH SYSTEM
oz, lb, ton
•
Distance
meter (m)
in, ft, yd, mi
•
Temperature
Kelvin (K)
°F
•
Time
second (s or sec)
•
Amount
mole (mol)
sec, min, hr, day
DERIVED QUANTITY (derived from the fundamental quantities above)
• Area (distance)2
m2
in2, ft2
•
Volume (distance)3
m3 , L
in3, yd3
•
Velocity (distance/time)
m/s
mi/hr
•
Density (mass/volume)
g/L
lb/in3
*See table 1.5 for metric prefixes! (Know Pico through Mega)
Temperature Scales
• Celsius to Kelvin conversion:
TK = T°C + 273
• Kelvin to Celsius conversion:
T°C = TK - 273
• Fahrenheit to Celsius conversion:
T°C = (T°F - 32) ÷ 1.8
• Celsius to Fahrenheit conversion:
T°F = (1.8 • T°C) + 32
Accuracy & Precision
Accuracy - how close
the measurement is
to the “true” value
Precision – how close
individual
measurements are to
each other.
Accuracy
PERCENTAGE ERROR (PE)
observed value - accepted (true) value
=
--------------------------------------- X 100%
accepted (true) value
How many significant digits are
there?
1.4563 cm
0.00123 m
1.0058 sec
1.54 x 1015m
8.500 mm
5003 km
100. L
5000 mL
Addition & Subtraction
5.42 cm
0.012 cm
 4.6 cm
10.0 cm
85063 mL
 6450 mL
78610 mL
Multiplying & Dividing
5.26400m x 0.00012m  .00063 m2
4500.2m

2.125 sec
2118 m/s
Dimensional Analysis
A problem solving method using a series of multiplications
and divisions
Multiply by fractions called “conversion factors”
ALL conversion factors are equal to 1
There is a table of conversion factors in the back cover of
your textbook
STEPS OF DIMENSIONAL ANALYSIS
1) put the given AND the given unit on the left
2) arrange conversion factors (fractions) to cancel ALL units
EXCEPT the required unit
For fractional units (m/sec)– work one unit at a time
For units to powers (m3) – take the ENTIRE conversion
factor to that power