Introduction to Physics

And the Metric System

Introduction to Physics• Physics is a natural science.

• Examines nature.• Seeks natural explanations.

• Concerned with mass, charge, energy, motion, force, etc.

• Seeks to understand how the universe behaves.

Introduction to Physics• Syllabus• Calendar• Classroom Policies• Lab Safety• Class Website• “Textbooks”

The Metric System• Based on powers of 10.

• 109 = 1 billion• 106 = 1 million• 103 = 1 thousand• 102 = 1 hundred• 10-2 = 1 / 100• 10-3 = 1 / 1000• 10-6 = 1 / 1 000 000• 10-9 = 1 / 1 000 000 000

Powers of Ten• 103 seems almost as large as 104.

• It’s NOT!• 104 is 10 times larger than 103.• Be careful when considering large

numbers.

mks vs cgs• mks = meter-kilogram-second

• Length meas. in meters.• Mass meas. in kilograms.• Time meas. in seconds.

• We’ll use this set of units most frequently.

• cgs = centimeter-gram-second• Length meas. in centimeters.• Mass meas. in grams.

Prefixes• Giga (G) x 109

• Mega (M) x 106

• kilo (k) x 103

• centi (c) x 10-2

• milli (m) x 10-3

• micro () x 10-6

• nano (n) x 10-9

Understanding Metric Scale• The MegaPenny Project

Significant Figures• Important in reporting answers

accurately and precisely.• A fig. is sig. if it is known or

estimated.

Significant Figures• Rule 1: All non-zero figs. are sig.

• 123 has 3 SF.• 1.23 also has 3 SF.

• Rule 2: “Sandwich” zeroes are sig.• 103 has 3 SF.• 2.002 has 4 SF.

Significant Figures• Rule 3: Trailing zeroes are sig. IF

the value contains a decimal.• 100 has 1 SF.• 10.0 has 3 SF.• 100. has 3 SF.• 2020 has 3 SF.• 202.0 has 4 SF.

Significant Figures• Rule 4: Leading zeroes are NEVER

sig.• 0.0020 has 2 SF.• 0.0154 has 3 SF.• 0.0101 has 3 SF.• 0.0003 has 1 SF.

Significant Figures• Rule 5: If a number is written in

sci. not., only the figs. in the base are sig.• 1.05 x 105 has 3 SF.• 2.0 x 1032 has 2 SF.• 1.6000 x 10-8 has 5 SF.

Significant Figures• Multiplying or Dividing Using SF.

• Answer has same number of SF as least precise number being multiplied/divided.

• EX: 2.05 grams / 1.1 mL• Calculator gives: 1.863636... g/mL• Round to 2 SF: 1.9 g/mL

• EX: 15.0 cm x 205.5 cm• Calculator gives: 3082.5 cm3

• Round to 3 SF: 3080 cm3

Significant Figures• Adding or Subtracting Using SF.

• Answer has the same number of decimal places as the least precise number being added/subtracted.

• EX: 2.15 m + 1.0 m• Calculator gives: 3.15 m• Round to 1 d.p.: 3.2 m

• EX: 4.49 s – 3.048 s• Calculator gives: 1.442 s• Round to 2 d.p.: 1.44 s