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Any data or value is expressed in terms of a number [quantity] and a unit [describing the type of measurement] Meet me in 5…. 5 minutes? 5 weeks?5 days?5 blocks from here? A number alone is meaningless: 2
I bought this great table. It is 45… 45 years old? 45 inches tall? 45 centimeters long? 3
Length meter Volume liquid Liter Mass gram 4
LENGTH = Distance from one point to another The base unit for length is METER [m] –1 kilometer [km] = 5 – 6 blocks –1meter [m] = from floor to door handle –1 centimeter [cm] = width of little finger –1 millimeter [mm] = width of a dime / pencil lead NOTICE THE ABBREVIATIONS: prefix and unit 5
VOLUME LIQUID = Amount of space that a liquid occupies The base unit for volume liquid is LITER [L] –4 liters [L] = 1 gallon –355 milliliter [mL] = 12 ounces NOTICE THE ABBREVIATIONS: prefix and unit 6
MASS [not to be confused with WEIGHT] = amount of matter that an object has or contains The base unit for mass is the GRAM [g] –1 kilogram [kg] = house brick – 1 gram [g] = 1 small paper clip –454 grams [g] = 1 pound NOTICE THE ABBREVIATIONS: prefix and unit 7
SO WHAT IS WEIGHT ??? It is a FORCE. The force exerted by gravity on any object. While Mass does NOT vary with location, WEIGHT varies depending on the gravitational pull. Where do you weigh the most? On the moon, or on Earth???? 8
Mass vs. Weight Can you hear me now? 9
Your weight in the Universe 10
TIME What time is it? Time relative to the rest of the Universe and everyone in it e.g. 3:00 pm Eastern time, on August 24 th, 2006 How much time? Quantity / interval between 2 events = how long does it take to …? e.g. it took 30 seconds to sharpen my pencil SI uses second, millisecond. The other accepted units, i.e. minutes, hours, days… are not multiplied by 10 11
TEMPERATURE = how hot or cold something is. [we will expand later] SI unit is Celsius [°C] and Kelvin [K] Note no degree symbol for Kelvin Water boils Water freezes °F°F Scale of 180 Fahrenheit 12
TEMPERATURE = how hot or cold something is. SI unit is Celsius [°C] and Kelvin [K] Note no degree symbol for Kelvin Water boils Water freezes °F°F °C°C Scale of 180 Scale of 100 CentigradeFahrenheit 13
TEMPERATURE = how hot or cold something is. SI unit is Celsius [°C] and Kelvin [K] Note no degree symbol for Kelvin Water boils Water freezes °F°F °C°C K K is the absolute zero. Even the atoms are stopped Scale of 180 Scale of 100 KelvinCentigradeFahrenheit Note 1 Kelvin = 1 °Celsius 14
Calculations Using Temperature Generally require temps in kelvins T (K) = t (˚C) Body temp = 37 ˚C = 310 K Liquid nitrogen = -196 ˚C = 77 K Generally require temps in kelvins T (K) = t (˚C) Body temp = 37 ˚C = 310 K Liquid nitrogen = -196 ˚C = 77 K 15
180°F = 9°F =1.8°F 100°C 5°C 1°C Zero point: 0°C = 32°F °F = 9/5 °C + 32 Fahrenheit Formula 16
Celsius Formula Rearrange to find T°C °F = 9/5 °C + 32 °F - 32 = 9/5 °C ( ) °F - 32 = 9/5 °C 9/5 9/5 9/5 9/5 (°F - 32) * 5/9 = °C 17
Temperature Conversions A person with hypothermia has a body temperature of 29.1°C. What is the body temperature in °F? °F = 9/5 (29.1°C) + 32 = = = 84.4°F 18
DERIVED UNITS Units that are found as the result of CALCULATONS 1.AREA: the surface of an object Formula = Length x Width Example: if you measure in meter, what will the unit be for the area?? NOTE: both dimensions / measurements must be in the same units 19
5 m 10 m AREA = 5 m x 10 m = The ‘derived’ unit is read as “square meter”… Numerical value 50m2m2 20
DERIVED UNITS Units that are found as the result of CALCULATONS 2.VOLUME solid: space that an object occupies or contains. Formula = Length x Width x Height Example: if you measure in centimeter, what will the unit be for the volume?? 21
3 cm 15 cm VOLUME = 3 cm x 5 cm x 15 cm = The ‘derived’ unit is read as “cubic centimeter”… Numerical value 225cm 3 5 cm 22
1 cubic centimeter = 1 millimeter ???? 1 mL of any liquid occupies [fills] a small container measuring 1cm by 1cm by 1 cm 1 cm So 1mL is equivalent to 1cm 3 23
What is the length of the sides of a cube that contains exactly 1 Liter? 24
DERIVED UNITS Units that are found as the result of CALCULATONS 3.DENSITY: how tightly the matter of an object is packed into a given volume It is an important physical property Which one weighs more, 1 kg of feather or 1 kg of nails??? Which one is less dense? 25
The mass is the same -1 kg-, but their volumes -the space that they occupy- are different. The feathers occupy more space, so they are less dense 26
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DERIVED UNITS DENSITY Formula = Mass divided by Volume Example: if the mass of your book is given in grams and its volume in cubic cm, what will the unit be for its density?? 28
Mass = 300 g Volume = 60 cm 3 DENSITY = 300 grams 60 cubic centimeter Divide numbers to get ½ of the answer Divide units to get the other ½ of the answer = 5 g/cm 3 ScienceScience 29
DENSITY = 5 g/cm 3 ScienceScience This derived unit is a new, more complex unit The ‘division’ slash is read as “per”… 30
Mercury 13.6 g/cm g/cm 3 Aluminum 2.7 g/cm 3 Platinum 31
7.8 g/cm 3 32 STEEL CORK GOLD OAK AIR 0.24 g/cm g/cm g/cm g/cm 3
Problem A piece of copper has a mass of g. It is 9.36 cm long, 7.23 cm wide, and 0.95 mm thick. Calculate density (g/cm 3 ). M VD
PROBLEM: Mercury (Hg) has a density of 13.6 g/cm 3. What is the mass of 95 mL of Hg in grams? PROBLEM: Mercury (Hg) has a density of 13.6 g/cm 3. What is the mass of 95 mL of Hg in grams? VD HIDE WHAT YOU ARE LOOKING FOR TO FIND THE RIGHT FORMULA M 34
REMEMBER: 1 cm 3 = 1 mL 35
When two values are multiplied, their units multiply also… (5.0 kilograms) (7.0 meters) = 35 Kg m The ‘derived’ unit is read as “kilogram meter” Numerical value = “x” symbol for multiplcation 36
Some more complex calculations may require both multiplication and division… (8.0 kg) (6.0 meters) = 12 sec 2 The ‘derived’ unit is read as “kilogram meter per square second”… Numerical value (2.0 sec) (2.0 sec) kg m For example, 37
(8.0 kg) (6.0 meters) = 12 Sec 2 When the ‘derived’ unit is complex, it may be assigned a ‘nickname’… (2.0 sec) (2.0 sec) kg m This unit is defined as a “ NEWTON ”… a unit of force. [like weight] = 12 Newtons 38