Presentation on theme: "Unit Outline--Topics What is Physics? Branches of Science"— Presentation transcript:
1 Unit Outline--Topics What is Physics? Branches of Science Science TermsScientific modelsMeasuring and UnitsPowers of Ten and conversionsGraphingExperimental DesignScience vs. TechnologyAnalyzing in Physics
2 Chapter 1ObjectivesList basic SI units and the quantities they describe.Using prefixes and powers of ten.Distinguish between accuracy and precision.Taking good measurementsUse significant figures in measurements and calculations.
3 INTERNATIONAL SYSTEM OF UNITS (SI units) Developed for the sake ofconsistencyease of understandingsharing data
4 BASE SI UNITS (standard units) Measured quantity
5 DERIVED UNITS Derived Units: Combinations of the 7 base units. ExamplesArea (length x width) m x m = m2Velocity (distance/time) = m/s50 m25 meters10 meters
6 This chart allows students to see the original standard and the current standard.
7 Numbers as Measurements Chapter 1Numbers as MeasurementsIn SI, the standard measurement system for science, there are seven base units.Each base unit describes a single dimension, such as length, mass, or time.The units of length, mass, and time are the meter (m), kilogram (kg), and second (s), respectively.Derived units are formed by combining the seven base units with multiplication or division. For example, speeds are typically expressed in units of meters per second (m/s).
8 100 meters MEASUREMENTS the number of units or value the unit Measurements consist of a number and a unit.Example100 metersthe number of units or valuethe unit
9 Dimensions and Units Chapter 1 Measurements of physical quantities must be expressed in units that match the dimensions of that quantity.In addition to having the correct dimension, measurements used in calculations should also have the same units.For example, when determining area by multiplying length and width, be sure the measurements are expressed in the same units.
10 Chapter 1ObjectivesList basic SI units and the quantities they describe.Using prefixes and powers of ten.Distinguish between accuracy and precision.Taking good measurements
11 Section 2 Measurements in Experiments Chapter 1SI PrefixesIn SI, units are combined with prefixes that symbolize certain powers of 10. The most common prefixes and their symbols are shown in the table.
12 Chapter 1ObjectivesList basic SI units and the quantities they describe.Using prefixes and powers of ten.Distinguish between accuracy and precision.Taking good measurements
13 Accuracy and Precision Section 2 Measurements in ExperimentsChapter 1Accuracy and PrecisionAccuracy is a description of how close a measurement is to the correct or accepted value of the quantity measured.Precision is the degree of exactness of a measurement.A numeric measure of confidence in a measurement or result is known as uncertainty. A lower uncertainty indicates greater confidence.
14 ACCURACYAccuracy is the extent to which a measurement approaches the true value.Actual Time:2:10 pmYour Time:2:05 pmYour accuracy is off by 5 minutes
15 Accuracy and Precision Precision is the degree of exactness for a measurement.It is a property of the instrument used.The length of the pencil can be estimated to tenths of centimeters.Accuracy is how close the measurement is to the correct value.
16 Errors in Measurement Instrument error Method error Instrument error is caused by using measurement instruments that are flawed in some way.Instruments generally have stated accuracies such as “accurate to within 1%.”Method errorMethod error is caused by poor techniques (see picture below).Make sure your line of sight is directly over the measurement.Measurement methods that improve precision and accuracy, such as:-not using the end of the meter stick (as was done in the picture on the last slide)-measuring a quantity several times and averaging the results-having different people measure the same quantity and averaging the results.
17 these darts show good accuracy accurate which paint ball mark is more accurate?less accurate- The bull’s eye represents the true value. - The darts represent three separate measurements
18 PRECISION Precision is the degree of exactness of a measurement. Based on the scale of the measuring instrument.Smallest tick marks represent millimeters (mm)
19 PRECISION VS. ACCURACY A B C D A—Good precision and accuracy B—Some accuracy and poor precisionC—Good precision and poor accuracyD—Poor precision and accuracy
20 Discussion QuestionWhen shooting free throws, is it better to be precise or accurate?
22 Chapter 1ObjectivesList basic SI units and the quantities they describe.Using prefixes and powers of ten.Distinguish between accuracy and precision.Taking good measurements
23 Measurements Dimension - the kind of physical quantity being measured Examples: length, mass, time, volume, and so onEach dimension is measured in specific units.meters, kilograms, seconds, liters, and so onDerived units are combinations of other units.m/s, kg/m3, and many othersScientists use the SI system of measurement.Ask students to suggest other examples of dimensions, specific units, and derived units. You may also want to discuss the advantages of using a common system of measurement.
24 How to Measure? Know how to operate the measuring instrument Which unit(s) is represented?What does each tick mark represent?Are there multiple scales?Did you zero out the instrument (if possible)Be skilled and patient enough to measure with the greatest detail possible
25 What do the tick marks represent on a meter stick? What unit is represented by the smallest tick mark on the meter stick?m?dm?cm?mm?*
26 What do the tick marks represent on a meter stick? What is the measurement?In mm?65 mmIn cm?6.5 cmIn dm?.65 dmIn m?0.065 m?
27 Why so many different units of measurement for the same quantity? Consider Mark and Suzy. They want to measure the length of a room.The quantity they are measuring is distance (measured quantity).They both measure length in units of feet (the length of one foot) This is their measuring units.One important detail: Mark’s foot is longer than Suzy’s foot.
28 Why so many different units of measurement for the same quantity? Mark measures the length of the room. So does Suzy. Will they have the same measurement? Why or why not? Who will have the longer measurement in feet?Mark’s measurement is 18 feet and Suzy’s is 23 feet.The length of a markfoot is not the same as the length of a suzyfoot.To compare the two different measurements, one unit must be converted into the other so that both measurements are proportional.Standardizing units means to select either the length of Mark’s or Suzy’s foot as the accepted length of the unit called a foot.