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Terminal Velocity Investigating Forces and Motion in our Universe Expedition 1 The Quest for Exactness Objectives • To accomplish your expedition goal successfully, you will need to Evaluate systems and standards of measurement. • Use measurements to describe objects in your environment. • Discover why SI units are critical for communication among scientists, engineers, industrial partners, and societies. • Explore how measurements derived from SI units can be used to further describe your physical environment. • Compare accuracy and precision when analyzing measurement results. • Assess how technological advancements to measurement tools impact society. • A model is any representation of an object or event used to explain the natural world. • When a scientist or engineer collects data, the information is generally first put into a data table • Scientists use graphs to turn these raw numbers into a visual representation. Common graphs include line, bar, and circle graphs. • http://gated.jason.org/gated/digital_library/pages/DigitalLibraryReso urceView.aspx?h=1&rpid=16330 • Measurement uses numbers to describe processes and events. • Length – the distance between two points, • Time – the interval between two events • Mass – the amount of matter in an object • Temperature – the amount of energy within a sample of matter • Electric current – the flow of charges • Amount of a substance – the number of atoms or molecules in a sample of material, and • Luminous intensity – the measure of light intensity coming from a source. • Metrology is the study of measurement. • Metrology is the study of measurement. • An estimate is an approximate measurement of an object or event The Metric System • The Metric System is a base-ten system • SI units are the current world standard for measurement. There are seven basic SI units. They are the meter, kilogram , second, ampere, kelvin, mole and candela. • Each unit is used to measure a particular quantity • Additionally, SI units can be combined to describe area, volume, density, speed, and acceleration. • Scientific prefixes allow us to reduce the number of zeros and make the figures more manageable. For example, 54,500,000,000 meters = 54.5 giga-meters, and 400,000,000,000 meters = 400 gigameters • Converting Metric Units • When you are converting from a big unit (like kilometers) to a smaller unit (like millimeters), you multiply. • When you are converting from a small unit (like millimeters) to a larger unit (like kilometers) you devide. U.S.Customary Units- used in only 3 countries? • The U.S. ______________, and ___________ • Derived units use more than one measurement at a time. Some examples include area, volume, density, speed, acceleration, and weight. • Area is the size of the surface of a two-dimensional object. • Volume is the amount of space something takes up. • Your body displaces, or pushes out, an amount of water equal to the volume of your body below the water line. • Speed is the change in distance over time. • Accelleration is the rate of the change in velocity. • Weight is the force exerted on any object with mass by the gravitational acceleration of a body such as a planet. • Mass is the amount of matter in something. Matter is anything that has mass and takes up space. Errors in Measurement • A standard is a benchmark used to compare other measures. Calibration is the process of determining how close a measured result is to the true value. • Accuracy is how close your measurement is to the actual value. • Precision is how close a group of measurement s are to each other. • Accuracy is how close your measurement is to the actual value. • Precision is how close a group of measurements are to each other. • Significant digits describe how precise a number is. There are several rules to follow when counting significant digits. • Class rule- only use 2 decimal points (unless otherwise instructed) Which ruler will result in greater precision if used to take repeated measurements? Why?