Post on 18-Dec-2015
Measurement
Measurements• science is based on
measurements• all measurements have:– magnitude– uncertainty– units
Numbers• mathematics is based
on numbers• exact numbers are
obtained by :– counting– definition
Measurements
• Measurements are not numbers– Numbers are obtained by counting or by
definition; measurements are obtained by comparing an object with a standard “unit”
– When you say that a table is 2 meters long, you are really saying that the table is two times longer than an object that is 1 meter long
Measurements
• Numbers are exact; measurements are inexact• Mathematics is based on numbers; science is
based on measurement
Uncertainty in Measurement
• Comparison with a unit or a scale of units always involves some uncertainty
• Estimate between the smallest scale divisions• The digit between the lines is always uncertain
(estimated)
Uncertainty in Measuring Devices
• There is a limit to the precision of a measurement
• The scientist making the measurement must decide the uncertainty value for a particular measuring device.
• See “Scale Reading, Uncertainty and Significant Figures”
Significant figures
• Significant figures are the digits in a measurement known with certainty plus one digit that is uncertain (estimated)