Chapter 1 2 Measurements in Physics SI Units

SI Units In 1960, an international committee decided on a system of standards and

Random Facts (will not be tested): Unit Original Standard Current Standard Meter (length) 1/10

These 7 SI units cannot explain everything though… These units have been combined to

Memorization time! You are required to know the following prefixes for units: a) Pico

Conversions • Example: Convert 162000 g to Mg • Example: Convert 1312 km to

Practice conversions 1) 10 kilograms in megagrams 2) 0. 00342 kilometers in centimeters 3)

Answers 1) 10 kilograms is 0. 01 megagrams 2) 0. 00342 kilometers is 342

Significant Figures • Significant figures (also called significant digits) are important as they indicate

Practice a) b) c) d) e) f) g) 1. 0303 m 2. 50 kg

Rules for addition and subtraction • When adding and subtracting numbers, the final answer

Rules for multiplication and division • When multiplying and dividing, the final answer must

Practice 1) 2) 3) 4) 5) 6) 7) 8) 97. 3 + 5. 85

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Chapter 1 -2: Measurements in Physics

SI Units In 1960, an international committee decided on a system of standards and units, known as SI units (Systeme International d’Unites). We have 7 base units in SI: 1) meter 2) kilogram 3) second 4) ampere 5) candela 6) kelvin and 7) mole

Random Facts (will not be tested): Unit Original Standard Current Standard Meter (length) 1/10 000 th the distance from the equator to the North Pole The distance travelled by light in a vacuum in 3. 33564095 x 10 -9 s Kilogram (mass) Mass of 0. 001 cubic meters of water The mass of a specific platinum-iridium alloy cylinder Second (time) (1/60)(1/24) = 0. 000 011 574 average solar days 9 192 631 770 times the period of a radio wave emitted from cesium-133 atom

These 7 SI units cannot explain everything though… These units have been combined to create what we call “derived units” Example: Velocity is measured in m/s (meters per second) Force is measured in N (Newton’s)

Memorization time! You are required to know the following prefixes for units: a) Pico (p): 10 -12 g) kilo(k): 103 b) Nano(n): 10 -9 h) mega(M): 106 c) Micro(μ): 10 -6 i) giga(G): 109 d) Milli(m): 10 -3 j) tetra(T): 1012 e) Centi(c): 10 -2 f) deci(d): 10 -1

Conversions • Example: Convert 162000 g to Mg • Example: Convert 1312 km to meters

Practice conversions 1) 10 kilograms in megagrams 2) 0. 00342 kilometers in centimeters 3) 132. 5 cm in decimeters 4) 132 millimeters to micrometers 5) 262523 micrometers in meters 6) 2329 picograms to milligrams **If the unit is growing larger, the number should get smaller**

Answers 1) 10 kilograms is 0. 01 megagrams 2) 0. 00342 kilometers is 342 centimeters 3) 132. 5 cm is 13. 25 decimeters 4) 132 millimeters is 132000 micrometers 5) 262523 micrometers is 0. 262523 meters 6) 2329 picograms is 0. 000002329 milligrams

Significant Figures • Significant figures (also called significant digits) are important as they indicate the precision of a measurement • Page 18 in your textbook has the rules for determining the amount of significant figures in a number

Practice a) b) c) d) e) f) g) 1. 0303 m 2. 50 kg 0. 00032 s 3. 0 x 102 mm 45 s 40 s 2. 2830 km h) 1000 kg i) 6. 723 m j) 4. 200 J

Rules for addition and subtraction • When adding and subtracting numbers, the final answer will have the same number of decimal places as the number used in the addition/subtraction that had the least number of decimal places. • Examples: 121. 03 + 5. 8 = 125 – 5. 5 =

Rules for multiplication and division • When multiplying and dividing, the final answer must have the same number of significant figures as the number used that had the least number of significant digits. Examples: a) 24. 0 x 1. 5 = b) 36. 00/2. 00 =

Practice 1) 2) 3) 4) 5) 6) 7) 8) 97. 3 + 5. 85 = 122. 3 – 0. 52 = (124. 2)(2. 1) = (2 x 102)(1. 232) = 24. 56 / 2. 3213 = 2. 02 x 106 + 1. 3 x 105 = 1. 000 + 2. 01 + 3. 523 + 2. 6 = (1. 20)(2. 212)(0. 0035) =