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Phys141 Principles of Physical Science Chapter 1 Measurement

Phys141 Principles of Physical Science Chapter 1 Measurement. Instructor: Li Ma Office: NBC 126 Phone: (713) 313-7028 Email: malx@tsu.edu Webpage: http://itscience.tsu.edu/ma Department of Computer Science & Physics Texas Southern University, Houston. Sept. 8, 2004. Measurement.

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Phys141 Principles of Physical Science Chapter 1 Measurement

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  1. Phys141 Principles of Physical ScienceChapter 1 Measurement Instructor: Li Ma Office: NBC 126 Phone: (713) 313-7028 Email: malx@tsu.edu Webpage: http://itscience.tsu.edu/ma Department of Computer Science & Physics Texas Southern University, Houston Sept. 8, 2004

  2. Measurement • Measurements in our daily life: • length/height • weight/mass • time • temperature • pressure • Others • First step to understand our physical environment • Describe the nature • Use our senses to make measurements

  3. The Senses • 5 senses make it possible to know the environment: • sight, hearing, touch, taste, smell: provide information • Limitations of sense: • for example, telescope to distinguish the stars, microscope for the cell • may also provide false information • can be reduced or eliminated by using measuring instruments • Instruments have their limitations: accuracy limits • Scientific method will tell us how to deal with them

  4. Systems of Units • Units • Express measurements • Describe things in a concrete way – that is, numerically • Standard unit • fixed and reproducible value for the purpose of taking accurate measurements • Systems of units • Metric system • British system

  5. Systems of Units (cont) • Fundamental physical quantities • length, mass, time, etc. • Length • Description of space: location/size • Measurement of space in any direction: length • “meter” in metric system • “foot” in British system

  6. Systems of Units (cont) • Mass • The amount of matter an object contains • Can be defined in terms of force and acceleration, and gravity • “kilogram” in metric system • Mass is fundamental quantity, not weight: Mass doesn’t change when measured in different place

  7. Systems of Units (cont) • Time • Duration, period, interval • The continuous, forward flowing of events • Only one direction – forward • The 4th dimension of the space • “second” in both metric system and British system

  8. More on Metric System • mks system • International Standard System (SI): 7 base units • Meter (m) • Kilogram (kg) • Second (s) • Ampere (A): measure the flow of electric charge • Kelvin (K): measure the temperature • Mole (mol): measure the amount of a substance • Candela (cd): measure luminous intensity

  9. More on Metric System (cont) • Metric prefixes • mega- (M): 1,000,000 (million) • kilo- (k): 1,000 (thousand) • centi- (c): 0.01 (hundredth) • milli- (m): 0.001 (thousandth) • cgs system: centimeter, gram, second • Decimal (base-10) system • Simpler when converting from one unit to another

  10. Derived Units

  11. Conversion Factors • Conversion Factor • Relate one unit to another: 1 in. = 2.54 cm • Ration from an equivalence statement • Steps for converting: • Step 1: choose a conversion factor • Step 2: cancel the unwanted unit • Step 3: check the remained unit

  12. Significant Figures • Rules for number of significant figures to keep in operations • In multiplying and dividing, the least number of significant figures • In adding and subtracting, the least number of decimal places • Rules for rounding • If the first digit to be dropped is less than 5, leave the preceding digit as it • If the first digit to be dropped is 5 or greater, increase the preceding digit by 1

  13. Scientific Notation • Power of 10 • 1000 = 1x103 = 1E3 • 26400000 = 2.64x107 = 2.64E7 • 0.00000264 = 2.64x10-6 = 2.64E-6 • Rules for using this notation • The exponent, or power of 10, is increased by 1 for every place the decimal point is shifted to the left • The exponent, or power of 10, is decreased by 1 for every place the decimal point is shifted to the right

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