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Physics Toolkit. Chapter 1 Glencoe Physics Principles & Problems. 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
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Physics Toolkit Chapter 1 Glencoe Physics Principles & Problems
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
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
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
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.
Graph Interpretation “Directly proportional” “Inversely proportional”
slope = rise / run • slope = 6 m/s / 4 s • slope = 1.5 m/s/s • (or slope = 1.5 m/s2)
Systems of measurement Weight = Mass x Acceleration* mks (meter-kg-sec) or International System (SI) cgs (cm-g-sec) *Acceleration due to gravity
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
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
Math relationships in equations F = G m1 m2 d2 F a m F a 1/d2
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
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 %
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"