Transcript Which group has the most accurate measurement?

Keith Baty
Whitehouse High School
How close a measurement agrees
with a true or accepted value.
How close several trials making
the same measurement are to
each other. The reproducibility of
data. Agreement among a set of
data.
Good accuracy
Poor accuracy
Poor accuracy
Good precision
Good precision
Poor precision
A metal bar about 9.8 inches long has been passed around to several
groups of students. Each group is asked to measure the length of the
bar. Each group has five students and each student independently
measures the rod and records his or her result.
Student
Group
Student
1
Student
2
Student
3
Student
4
Student
5
Group A
10.1
10.4
9.6
9.9
10.8
Group B
10.135
10.227
10.201
10.011
10.155
Group C
12.14
12.17
12.15
12.14
12.18
Group D
10.05
10.82
8.01
11.5
10.77
Group E
10
11
10
10
10
Which group has the most accurate
measurement?
A metal bar about 9.8 inches long has been passed around to several
groups of students. Each group is asked to measure the length of the
bar. Each group has five students and each student independently
measures the rod and records his or her result.
Student
Group
Student
1
Student
2
Student
3
Student
4
Student
5
Group A
10.1
10.4
9.6
9.9
10.8
Group B
10.135
10.227
10.201
10.011
10.155
Group C
12.14
12.17
12.15
12.14
12.18
Group D
10.05
10.82
8.01
11.5
10.77
Group E
10
11
10
10
10
Which group has the most precise
measurement?
Suppose a ruler is used to measure the length of an object as
shown in the figure below.
Similarly, all measured quantities are generally reported
in such a way that the last digit is uncertain. All digits in
a measurement including the uncertain one are called
significant figures.
Counting Significant Figures
• The following rules can be used to
determine the number of significant
figures (or digits).
• All non-zero digits are considered
significant.
• If a zero is between two non-zero digits
then it is significant.
• Leading zeros are never significant.
• Trailing zeros are only significant if there
is a decimal present.
Examples
Measured
Value
2.456
1003.2
1.03000
0.0000402
230000
# of S. F.
4
5
6
3
?
Exact numbers are considered to have an infinite
number of significant figures. For example, if you said,
“A is twice (or two times) as large as B”, the number 2
would be exact. Or, if you said “There are 4 quarts in a
gallon”, the number 4 would be exact. Exact numbers
usually involve counted values or definitions.
Multiplication and division
For multiplication and division, the number of
significant figures in the answer should be equal to
the number of sig figs as the measurement with the
least number of SIGNIFICANT FIGURES.
2.7832
x 1.4
3.89648
round off to 3.9
Examples:
3.40 x 4.5672 = 15.52848
3
5
round off to 15.5
(3 significant figures)
Addition and subtraction
The result should be reported to the same
number of decimal places as the least precise
measurement (the measurement with the
fewest decimal places).
3.6923
 1.234
 2.02
6.9463
round off to 6.95
8.7937
 2.123
6.6707
round off to 6.671
Example:
2.487 + 330.4 + 22.59 = 355.477
round off to 355.5
(Uncertainty in tenths place)
9. The following are placed in a beaker weighing
39.457 g: 2.689 g of NaCl, 1.26 g of sand and 5.0 g
water . What is the final mass of the beaker?
10. If the beaker containing a sample of alcohol
weighs 49.8767 g and the empty beaker weighs
49.214 g, what is the weight of the alcohol?
CONVERSION
FACTORS
mega (M) 1 Mm = 106 m
kilo (k) 1 km = 1000 m
hecto (h) 1 hm = 100 m
deka (da) 1 dam = 10 m
English
/Metric
1 in = 2.54 cm
1.06 qt = 1 L
1 lb = 454 g
meter (m)
liter (L)
gram (g)
deci (d) 10 dm = 1 m
centi (c) 100 cm = 1 m
nano (n) 109 nm = 1 m
milli (m) 1000 mm = 1 m
micro (μ) 106 μ m = 1 m
When I say I want to lose
weight I should say I want to
lose mass. I would weigh less
on the moon. The problem is I
would look the same in a
mirror. I really want there to be
less of me not less force of
gravity on me
Mass a measure of the amount of
matter
Weight a measure of the force of
gravity on an object
Volume a measure of the amount of
space an object occupies