The Science of Physics
Measurements in Experiments
Numbers as Measurements
• To be of value, a measurement must have two parts in addition to the number
– ______– what kind of quantity
• Length, mass, time
– ______– how much of the quantity
• Meter, kilogram, second
SI System
• ______
• Used worldwide in science
• ______base units, each describing a single dimension
• Units combine to form a ______unit
– Liter, Newton, Joule, o Celcius
SI Prefixes
• Used to accommodate extremes
– Very large and small numbers
• Can also use scientific notation
SI System
• Both ______and ______must agree
– Length is in meters, not in kilograms
• When doing calculations with one dimension
– Prefixes must be the ______
• Area=length*width
• m*m not m*cm
– 25m*10m not 25m*1000cm
• ______– describes how close a measured value is to the true value of the quantity measured
• ______– refers to the degree of exactness with which a measurement is made and stated
– How many ______places there are
– Do all of the ______agree with one another
Significant Figures
• Use ______to keep track of imprecision
• Significant figures – those digits in a measurement that are known with certainty plus the first digit that is uncertain
• When the last digit in a measurement is ______, it is difficult to tell if the zero is significant or not
– You can use ______to show that a zero is significant
• Rules for Significant Figures
– All ______digits are significant. (1-9)
– Zeroes ______significant digits are significant. (101, zero is significant)
– Zeroes ______the decimal are significant if there is a non-zero number in front of them. (3.40, zero is significant)
• Rules for Significant Figures
– If there is a ______, zeroes at the end of a number are significant. (50. zero is significant)
– Zeroes at the ______of a number are not significant. (0.003, zeroes are not significant)
– If there is _____ decimal point, zeroes at the ______of a number are ______. (60, zero is not significant)
Rules for Calculating With Significant Figures
• Addition and Subtraction – answer should have same number of ______as the least amount of decimal places in the measurement
• Multiplication and Division – answer should have the same number of ______as the measurement with the least amount of significant figures
Rules for Rounding
• Round ______– 0-4
• Round ______– 6-9
• Special Rules for 5
– Round to the nearest even number if nothing follows the five (32.25~32.2 or 54.75~54.8)
– Round up if there are digits following the 5 (54.7511~54.8)