1 / 18

Physics and Physical Measurement

Physics and Physical Measurement. The Realm of physics Measurement and uncertainties. The Realm of Physics. Range of magnitudes of quantities in our universe: Visible universe= 10 25 m The age of the universe= 10 18 s The total mass of the universe= 10 50 kg The atom:

willa
Download Presentation

Physics and Physical Measurement

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Physics and Physical Measurement The Realm of physics Measurement and uncertainties

  2. The Realm of Physics • Range of magnitudes of quantities in our universe: • Visible universe= 1025 m • The age of the universe= 1018 s • The total mass of the universe= 1050 kg • The atom: • The diameter of an atom = 10-10 m • The diameter of the nucleus = 10-15 m

  3. Upper and lower measurements • Planck length 10-35 m (lower) • Speed of light in a vacuum 3 x108 m/s • Time = distance/ speed • Time= 10-35 m/ 108 m/s • Time= 10-43 s • If quarks are the fundamental unit then their mass would give us the lower limit, but they hide in protons and our best guess is 10-30 kg. This is also the approximate mass of an electron at rest.

  4. Stating ratios as differences in magnitude • 10-10m/ 10-15 m= 105 • 105 is known as a difference of five orders of magnitude. What is the order of magnitude of the diameter of a proton? A. 10-12 m B. 10-15 m C. 10-18 m

  5. Estimating Approximate Values • Estimate the value of these everyday quantities to one or two significant figures. • How high is a two storey house in meters? • What is the diameter of your pupil? • How many times does your heart beat in an hour when you are relaxed? • What is the weight of an apple in Newtons?

  6. Fundamental Units • Meter m length • Kilogram kg mass • Second s time • Ampere A electric current • Kelvin K temperature • Mole mol amount of matter • Candela cd intensity of light

  7. Mechanics and Derived Units • Mechanics is the study of matter, forces, and energy. With combinations of the first three base units (m, kg, and s), all other units for mechanics can be developed. • Newton N force or weight kg m s-2 • Joule J energy or work kg m2 s-2 • Watt W power kg m2 s-3 • Pascal Pa pressure kg m-1 s-2

  8. Derived Units Find the symbol, concept, and broken down base units for each of the following: • Hertz • Coulumb • Ohm • Tesla • Weber • Becquerel

  9. Problems • Give units for the following expressed as derived and base units: • Force b. Kinetic energy • Check if these equations work by substituting units into them. • Power= work/time or energy/time • Power = force x velocity

  10. Answers 1. a. N or kg m s-2 • J or kg m2 s-2 2. a. W: J s-1 or W: (kg m2 s-2 )s-1 or W: kg m2 s-3 b. W: N x (m s-1 ) or W: (kg m s-2 )x (m s-1 ) or W: kg m2 s-3

  11. Problems 3. Which one of the following units is a unit of energy? a. eV b. W s-1 c. W m-1 d. N m s-1 4. Which on of the following lists a derived unit and a fundamental unit?

  12. Answers • eV • B

  13. Other Units

  14. Problem • Convert these units to SI: a. Year b. 100 oC c. kWh d. eV

  15. Modifying SI Units • SI units can be modified by the use of prefixes.

  16. Problems • Change 2360000J to scientific notation and MJ. • A popular radio station has a frequency of 1090000Hz. Change this to scientific notation and MHz. • The average wavelength of white light is 5.0x 10-7 m. What would this be in nanometers? 9. The time taken for light to cross a room is about 1 x10-8 s. Change this into microseconds.

  17. Answers • 2.36 x 106 J or 2.36 MJ • 1.09 x 106 Hz or 1.09 MHz • 500 nm • 0.01 μs

  18. Uncertainty and Error • There are two types of errors: • Random and systematic • Random errors can be reduced by repeating measurement many times. • Systematic errors can be reduced by repeating measurement using a different method or different apparatus and comparing the results.

More Related