Lab # 1

Dimensions and UnitsDimensions and Units

Dimensions and UnitsDimensions 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

Unit Metric System FPS British Engineering System

Length m, cm Inch (in) Feet (ft) Feet (ft)

Mass Kg, g Pounds (lb) Slug

Time Seconds (s) Seconds (s) Seconds (s)

Force Dyne Poundal Pound weight

Area (m2, cm2) (ft2) (in2) ----

Volume cm3 Ft3 ----

Density gm/ cm3 lb/ ft3 ----

Heat (cal) (Kcal) (J) British Thermal Units (BTU)

----

Temperature Celsius (°C) and Kelvin (K) Fahrenheit (°F) ----

Pressure dyne/cm2 lb/inch2 ----

Viscosity gm/cm.sec lb/ft.sec

MEASUREMENTSMEASUREMENTS Metric English

LengthLength meter inches, feet

m in ft

Area is defined as length x width.

AreaArea square meter square feet

m2 ft2

Volume is defined as length x width x height .

VolumeVolume Liter or cubic centimeter gallon, cubic ft

L cm3 gal ft3

Mass - Time

A A balancebalance is used to measure mass in the is used to measure mass in the laboratory.laboratory.

Metric English

MassMass gramgram pounds/slugpounds/slug

g g lb lb

TimeTime is measured is measured the samethe same in both systems. in both systems. A clock, wristwatch, or stopwatch will be A clock, wristwatch, or stopwatch will be used in the laboratory.used in the laboratory.

Time Time seconds hour minutes s hr min

ForceMetric 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 oF (32 - 212) oF = (1.8 oC) + 32– Celsius oC (0 -100) oC = (oF - 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 oK K = oC + 273– Rankine oR R = oF + 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 = 4.184 J

PressurePressure: Is the force per unit area.Metric Englishdyne/cm2 lb/in2

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/in2)

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: PoiseMetric English

dyne.sec/cm2 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 = 30.48 cm 1 foot = 12 inMass 1 lb = 16 ounce 1 lb = 453.6 g 1 lb = 7000 grains

1 ton = 2000 lb 1 kg = 2.2 lb

Volume 1 L = 61.025 cubic inch 1 cubic foot = 28.32 L 1 US gallon = 3.785 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

CONVERSIONSCONVERSIONS

Convert the following:

65.9 lb kg

Looking up the conversion, there are 2.2 lb

for every 1 kg.

65.9 lb = 30.0 kg30.0 kg

2.2

PROBLEMSPROBLEMS

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

PROBLEMSPROBLEMS

2- Find the temperature in Fahrenheit scale

corresponding to 90 degree C on the

centigrade scale

Solution:

oF = (1.8 X oC) + 32

oF = (1.8 X 90) + 32

oF = 194

PROBLEMSPROBLEMS

3- Determain the number of poises equivalent to

12 lb/ft.sec.

Solution:

Poise = 12 X 454 / 1 X 1/30.48 = 178.58

PROBLEMSPROBLEMS

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

PROBLEMSPROBLEMS

5- A pressure gauge in a system reads 100 psi.

what is the absolute pressure

Solution:

1 Absolute pressure= Atmospheric pr. + Gauge pr.

14.7+100=114.7 psi

Thank You