Lab # 1 Dimensions and Units

There are different types of measurements that can be made in the laboratory like mass, time, volume, and length. There are two different systems of units and dimensions: The metric system The English system The first step to understanding measurements is to learn the types, symbols, & units associated with these measurements.

MEASUREMENTS There are different types of measurements that can be made in the lab for length, mass, volume, temperature, area, time, heat and pressure. British System UnitMetric SystemFPSBritish Engineering System Lengthm, cmInch (in) Feet (ft)Feet (ft) MassKg, gPounds (lb)Slug TimeSeconds (s) ForceDynePoundalPound weight Area(m 2, cm 2 )(ft 2 ) (in 2 )---- Volumecm 3 Ft Densitygm/ cm 3 lb/ ft Heat(cal) (Kcal) (J)British Thermal Units (BTU) ---- TemperatureCelsius (°C) and Kelvin (K)Fahrenheit (°F)---- Pressuredyne/cm 2 lb/inch Viscositygm/cm.seclb/ft.sec

MEASUREMENTS Metric English Length Lengthmeter inches, feet m in ft Area is defined as length x width. Area Area square meter square feet m 2 ft 2 Volume is defined as length x width x height. Volume Volume Liter or cubic centimeter gallon, cubic ft L cm 3 gal ft 3

Mass - Time A balance is used to measure mass in the laboratory. Metric English Mass gram pounds/slug g lb g lb Time is measured the same in both systems. A clock, wristwatch, or stopwatch will be used in the laboratory. Time Time seconds hourminutes s hr min

Force Metric English Dyne Poundal Pound weight Dyne: The force required to accelerate a mass of one gram at a rate of one centimetre per second per second 1 dyne = 1 g·cm/s² Poundal: The force required to accelerate a mass of one lb at a rate of one foot per second per second

Density- Specific Gravity Density: The mass per unit volume at a fixed temperature and pressure. Density = Mass / Volume Specific gravity: The ratio of the density of a substance to the density of water. For liquids heavier than water: specific gravity = 145/(145 - °Bé) For liquids lighter than water: specific gravity = 140/(130 + °Bé) Specific Volume: The volume per unit mass.

TEMPERATURE Temperature is measured with a thermometer. –Standard Scales: Use the freezing and boiling points of water at atmospheric pressure as basis. –Fahrenheit o F ( ) o F = (1.8 o C) + 32 –Celsius o C (0 -100) o C = ( o F - 32)/1.8 –Roamer sys. (0 - 80) –Absolute scale: A scale having absolute zero as the lowest temperature. Absolute temperature scales only have positive numbers. –Kelvin o K K = o C –Rankine o R R = o F + 460

Heat Energy Energy: The condition of a body which gives it the capacity of doing work One Calorie: The amount of heat necessary to raise the temperature of 1g of water by one degree C. One British Thermal unit: The amount of heat necessary to raise the temperature of 1 lb of water by one degree F. Heat energy is usually measured in calories (cal) or joules (J). 1 cal = J

Pressure Pressure: Is the force per unit area. Metric English dyne/cm 2 lb/in 2 Gauge Pressure Pressure above the atmospheric pressure. Absolute Pressure The sum of the available atmospheric pressure and the gauge pressure. Absolute Pressure = Gauge Pressure + Atmospheric Pressure Standard atmospheric pressure A unit of pressure, defined as being equal to 760 mmHg 30 inHg 14.7 PSI (lb/in 2 )

Vacuum Used to describe the region of pressure below one atmosphere of Pressure referred to as negative pressure When speaking of vacuum, one must remember it as the opposite of pressure High vacuum means low pressure Absolute Pressure = Atmospheric Pressure – Vacuum Reading

Viscosity Measure of the resistance of a liquid to flow. Unit: Poise Metric English dyne.sec/cm 2 lb/ft.sec gm/cm.sec

Viscosity Kinematic Viscosity Kinematic viscosity can be obtained by dividing the absolute viscosity of a fluid with it's mass density ν = μ / ρ ν = kinematic viscosity μ = absolute viscosity ρ = density Unit: Stoke and centistokes

Since two different measuring systems exist, a scientist must be able to convert from one system to the other. Length  1 in = 2.54 cm  1 foot = cm  1 foot = 12 in Mass  1 lb = 16 ounce  1 lb = g  1 lb = 7000 grains  1 ton = 2000 lb  1 kg = 2.2 lb Volume  1 L = cubic inch  1 cubic foot = L  1 US gallon = L = 4 quarts CONVERSIONS

Since two different measuring systems exist, a scientist must be able to convert from one system to the other. Force  1 gram eight = 981 dynes  1 pound weight = 32.2 poundals  1 poundal = 13.8 dynes Heat  1 BTU = 252 calories  1 BTU = 778 ft.lb CONVERSIONS

CONVERSIONS Convert the following: 65.9 lb  kg Looking up the conversion, there are 2.2 lb for every 1 kg kg 65.9 lb = 30.0 kg 2.2

PROBLEMS 1- Find the specific gravity in degree Baume for a liquid having a specific gravity of 1.5 Solution: For liquids heavier than water: Sp. Gravity = 145/(145 - °Bé) 1.5 X (145 - °Bé) = 145 °Bé = 48.33

PROBLEMS 2- Find the temperature in Fahrenheit scale corresponding to 90 degree C on the centigrade scale Solution: o F = (1.8 X o C) + 32 o F = (1.8 X 90) + 32 o F = 194

PROBLEMS 3- Determain the number of poises equivalent to 12 lb/ft.sec. Solution: Poise = 12 X 454 / 1 X 1/30.48 =

PROBLEMS 4- Express 12 BTU of heat energy at work to mechanical energy units Solution: 1 BTU = 252 calories 12 BUT = 12 X 252 = 3024 calories

PROBLEMS 5- A pressure gauge in a system reads 100 psi. what is the absolute pressure Solution: 1 Absolute pressure= Atmospheric pr. + Gauge pr =114.7 psi

Thank You