Transcript Significant digits, base, and derived units

Significant digits, base, and
derived units
CMA High school
Base units of the metric system
Base quantity
Length
mass
Time
Temperature
Amount of a
substance
Electric current
Luminous
intensity
Base unit
meter
kilogram
second
kelvin
mole
symbol
m
kg
s
K
mol
ampere
candela
A
cd
Derived units
• Derived units are combinations of base
units.
• Examples: speed= m/s
• Density = kg/m3
• Momentum = kg m/s
• Force = kg m/s2= Newton
Significant digit rules
• Nonzero digits are always significant
• All final zeros after the decimal point are
significant
• Zeros between two significant digits are
significant
• Zeros used solely as placeholders are not
significant
Examples:
•
•
•
•
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305940 = 5 sig digs
3.5000 = 5 sig digs
0.0000000000500 = 3 sig digs
4.002 = 4 sig digs
0.000000002 = 1 sig dig
120000000000 = 2 sig digs
Adding and subtracting sig digs
• Line up numbers with the decimal to add
or subtract, then round the answer to the
smallest number of significant digits after
the decimal that you started with.
• 24.686m + 2.343m + 3.21 m = 30.239 m
• Round the answer to 30.24 m
Multiplying and dividing sig
digs
• After multiplying or dividing, round your
answer up to the smallest total number of
significant digits that you started with. (
Don’t pay attention to the decimal)
• 3.22 cm x 2.1 cm = 6.762 cm2, round up to
6.8 cm
• 4596/ 1 = 4596, round your answer to 5000
Homework/ classwork
• http://lectureonline.cl.msu.edu/~mmp/appli
st/sigfig/sig.htm