using scientific measurements
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Using Scientific Measurements. Uncertainty in Measurements. All measurements have uncertainty. Measurements involve estimation by the person making the measurement. Measuring devices are limited in their precision. Accuracy and Precision. - PowerPoint PPT PresentationTRANSCRIPT
Using Scientific Measurements
Uncertainty in Measurements
All measurements have uncertainty.
1. Measurements involve estimation by the person making the measurement.
2. Measuring devices are limited in their precision
Accuracy and PrecisionAccuracy – the
closeness of measured values to the true or accepted value
Precision – the closeness of repeated measurements of the same quantity
Percent Error• Used to compare measured values to the
true or accepted value.
%100xvalueaccepted
valueAcceptedValueMeasured
Percent ErrorSample Problems
1. Calculate the percent error in a length measurement of 4.25 cm if the correct value is 4.08 cm.
2. The actual density of a certain material is 7.44 g/cm3. A student measures the density of the same material as 7.30 g/cm3. What is the percent error of the measurement
Counting Significant FiguresDetermine the number of significant figures in each
of the following numbers:
0.003042
1.4030
1000
1000.
1000.00
0.060
50.0
10.47020
250.
65,321
2.00 x 102
1.004 x 105
Rounding to Significant FiguresRound each of the following numbers to three
significant digits:
1,566,311
2.651 x 10-3
84,592
0.0011672
0.07759
Calculations with significant figures
1. Find the volume of a cube that is 3.23 cm on each edge.
2. What is the sum of 67.14 kg and 8.2 kg?
3. Calculate the density of a 17.982 g object that occupies 4.13 cm3.