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Understanding Physics: Key Concepts in Measurement and Analysis

This chapter introduces fundamental concepts in physics, focusing on SI base units, significant figures, and graph interpretation. Learn how to determine relationships from graph shapes, perform metric and English conversions, and apply dimensional analysis. Gain insight into mathematical equations and their applications, including order of magnitude and percent error. Basic statistics in physics, including mean, median, and mode, are also explored, ensuring a comprehensive understanding of measurements and data analysis.

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Understanding Physics: Key Concepts in Measurement and Analysis

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  1. Physics Toolkit Chapter 1 Glencoe Physics Principles & Problems

  2. Learning Objectives • Know the SI system base units • Know what significant figures are and how to determine s.f. for multiplication/division and addition/subtraction • Read a graph to find slope • From graph shapes determine relationships • Convert within the metric system & to English system & vice versa • Convert using dimensional (unit) analysis • From math equations, determine relationships • Solve problems using order of magnitude and percent error • Basic statistics

  3. Assignments for Ch 1 • Read notes online • Read chapter 1 and write Reflections (see your syllabus) • Questions and problems from book: 1-12, 30, 31, 36-38, 42,45,46, 67-74

  4. International System (SI) A. Quantities and base units of measure • length – meter, m • temperature – Kelvin • mass – gram • time – second B. Derived quantities and units • electric current – ampere • weight – force with which gravity pulls on a quantity of matter – Newton is the unit

  5. Significant figures – determined by the equipment used to collect data. • Numbers are read directly from the equipment plus 1 estimated digit. • When multiplying several numbers, the number with the least significant digits determines how many digits are written in the answer. • Sample: 2.45 cm x 3.0052 cm x 1.004 cm. 2.45 has only 3 significant figures so the answer will also. • The answer is 7.39219096. Round to 7.39 cm3.

  6. Graph Interpretation “Directly proportional” “Inversely proportional”

  7. slope = rise / run • slope = 6 m/s / 4 s • slope = 1.5 m/s/s • (or slope = 1.5 m/s2)

  8. Systems of measurement Weight = Mass x Acceleration* mks (meter-kg-sec) or International System (SI) cgs (cm-g-sec) *Acceleration due to gravity

  9. English to Metric Conversion problem Convert your weight to metric weight where 1 kg = 2.2 lb. 130 lb 1 kg = 59 kg 2.2 lb Using weight = mass x gravity mg = 59kg(9.8m/s2) = 578.2 = 5.8 x 102 n

  10. Conversions Weight: 2.2 lb = 1kg Length: 1.0 in = 2.54cm 5280 ft = 1 mile 0.625 mile = 1 km Volume: 1.06 qt = 1.0 L 30. mi = ? Km gal L Unit analysis 30. mi 1km 1 gal 1.06 qt = 12.72 = 13 = 1.3 x 101 km gal 0.625 mi 4 qt 1 L L

  11. Math relationships in equations F = G m1 m2 d2 F a m F a 1/d2

  12. Order of Magnitude - solving problems by using powers of 10 800,000 (4200) 0.0026 (0.00097) 106 (103) = 109 = 109-(-6) 10-3 (10-3) 10-6 Answer: 1015

  13. Percent Error A chemist tests the boiling temperature of a chemical and finds it to be 137.2oC. The accepted value is 135.9oC. What is the percent error? % Error = / Vo - Va/ x 100 = 137.2oC - 135.9oC Va 135.9oC % Error = 0.9566 %

  14. Basic statistics • Mean, x - arithmetic average (not used in stats involving income - influenced by extreme values) • Median - middle value (used with salaries) • Mode - most common value (shoe stores purchase most common sizes) • Sample: test scores of 94,96,98,96 (your grades in Physics!) Mean, x = 94+96+98+96 = 96 4 Median = 96  middle Mode = 96  most common x is pronounced “x bar"

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