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Unit Outline--Topics

Unit Outline--Topics. What is Physics? Branches of Science Science Terms Scientific models Measuring and Units Powers of Ten and conversions Graphing Experimental Design Science vs. Technology Analyzing in Physics. Objectives. Chapter 1.

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Unit Outline--Topics

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  1. Unit Outline--Topics • What is Physics? • Branches of Science • Science Terms • Scientific models • Measuring and Units • Powers of Ten and conversions • Graphing • Experimental Design • Science vs. Technology • Analyzing in Physics

  2. Objectives Chapter 1 • List basic SI units and the quantities they describe. • Using prefixes and powers of ten. • Distinguish between accuracy and precision. • Taking good measurements • Use significant figures in measurements and calculations.

  3. INTERNATIONAL SYSTEM OF UNITS (SI units) • Developed for the sake of • consistency • ease of understanding • sharing data

  4. BASE SI UNITS (standard units) Measured quantity

  5. DERIVED UNITS • Derived Units: Combinations of the 7 base units. • Examples • Area (length x width) m x m = m2 • Velocity (distance/time) = m/s 50 m2 5 meters 10 meters

  6. Chapter 1 Numbers as Measurements • In 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).

  7. MEASUREMENTS • Measurements consist of a number and a unit. • Example 100 meters the number of units or value the unit

  8. Chapter 1 Dimensions and Units • 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.

  9. Objectives Chapter 1 • List basic SI units and the quantities they describe. • Using prefixes and powers of ten. • Distinguish between accuracy and precision. • Taking good measurements

  10. Section 2 Measurements in Experiments Chapter 1 SI Prefixes In SI, units are combined withprefixesthat symbolize certainpowers of 10.The most common prefixes and their symbols are shown in the table.

  11. Objectives Chapter 1 • List basic SI units and the quantities they describe. • Using prefixes and powers of ten. • Distinguish between accuracy and precision. • Taking good measurements

  12. Section 2 Measurements in Experiments Chapter 1 Accuracy and Precision • Accuracy 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.

  13. ACCURACY • Accuracy is the extent to which a measurement approaches the true value. Actual Time: 2:10 pm Your Time: 2:05 pm Your accuracy is off by 5 minutes

  14. 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.

  15. Errors in Measurement • Instrument 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 error • Method error is caused by poor techniques (see picture below).

  16. - The bull’s eye represents the true value.- The darts represent three separate measurements these darts show good accuracy accurate which paint ball mark is more accurate? less accurate

  17. PRECISION • Precision is the degree of exactness of a measurement. • Based on the scale of the measuring instrument. Smallest tick marks represent millimeters (mm)

  18. PRECISION VS. ACCURACY A B C D • A—Good precision and accuracy • B—Some accuracy and poor precision • C—Good precision and poor accuracy • D—Poor precision and accuracy

  19. Discussion Question • When shooting free throws, is it better to be precise or accurate?

  20. It’s better to be accurate.

  21. Objectives Chapter 1 • List basic SI units and the quantities they describe. • Using prefixes and powers of ten. • Distinguish between accuracy and precision. • Taking good measurements

  22. Measurements • Dimension - the kind of physical quantity being measured • Examples: length, mass, time, volume, and so on • Each dimension is measured in specific units. • meters, kilograms, seconds, liters, and so on • Derived units are combinations of other units. • m/s, kg/m3, and many others • Scientists use the SI system of measurement.

  23. 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

  24. 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? *

  25. What do the tick marks represent on a meter stick? • What is the measurement? In mm? 65 mm In cm? 6.5 cm In dm? .65 dm In m? 0.065 m?

  26. 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.

  27. 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.

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