Measurement

Measurement

In this chapter we will explore the following concepts:

1. Measurement of a physical parameter

2. Units, systems of units

3. Basic units in mechanics

4. Changing units

Stating a Measurement

In every measurement there is

a

¨ Number

followed by a

¨ Unit from measuring device

Standards of Measurement

When we measure, we use a measuring tool to compare some dimension of an object to a standard.

SOME TOOLS FOR MEASUREMENT

Basic & Derived Quantities

Basic Quantity Must be defined in terms of a standard (meter, kilogram, second).

Derived Quantity Defined in terms of combinations of basic quantities

Unit of speed = meter/second = m/s

International System of Units:In this system the units for the base quantities are:

Parameter Unit Name Symbol

Length meter m

Mass kilogram kg

Time second sec or s

Unit of Length: the Meter

A meter is a unit of length, currently defined as the distance light travels within 1/299782458th of a second.

Time Unit –second (s)The time needed for a cesium-133 atom to perform 9,192,631,770 complete oscillations

Volume Unit – the Liter (L)

1 gallon = 4 quarts

1 liter (L) = 1.06 quart

1 quart = 946 mL

1 L = 10 deciliters (dL)

= 100 centilliters (cL)

= 1000 milliliters (mL)

Volume is the amount of space occupied by a substance.

S.I unit of volume is liter (L).

The milliliter (ml) is commonly used for measuring smaller volumes of fluids.

Mass

The mass of an object is a measure of the

quantity of material it contains.

In the SI system, the mass unit is the

kilogram (kg).

In the metric system, the mass unit is the

gram (g).

Compare to US weight units:

1 kg = 2.20 lbs

1 lb = 454 grams

Temperature Scales

The degree of hotness or coldness is called temperature.

The S.I unit of temperature is kelvin

Other Scales:1. Celsius (C) scale

2. Fahrenheit (F) scale

1 C = 1.8 F

Other Systems of Units

CGS centimeter-gram-second

FPSfoot-pound-second

From the previous slide, state the tool (s) you would use to measureA. temperature ____________________B. volume ____________________

____________________C. time ____________________D. weight ____________________

Learning Check

From the previous slide, state the tool (s) you would use to measure

A. Temperature thermometerB. Volume measuring cup, graduated

cylinderC. Time watch, clocksD. Weight spring balance

Unit conversions

We will work exclusively in SI (MKS) units!

Unit Conversion

What are some S.I units that are used to measure each of the following?

A. length

B. volume

C. weight

D. temperature

Learning Check

Some possible answers are

A. length inch, foot, yard, mile

B. volume cup, teaspoon, gallon, pint,

quart

C. weight ounce, pound (lb), ton

D. temperature °F

Units in the Metric System

length meter m

volume liter L

mass gram g

temperature Celsius °C

Learning Check

Identify the measurement in metric units. A. John’s height is1) 1.5 yards 2) 6 feet 3) 2 meters

B. The volume of Pepsi in a big bottle is1) 1 liters 2) 1 quart 3) 2 pints

C. The mass of a lemon is1) 12 ounces 2) 145 grams 3) 0.6

pounds

Solution

A. John’s height is3) 2 meters

B. The volume of Pepsi in a big bottle is

1) 1 liter

C. The mass of a lemon is2) 145 grams

Changing Units

Units of Volume:• The SI unit of volume is the cubic meter (m)3.

• A more convenient unit of volume for everyday use is the liter, a non-SI unit.

• A liter (L) is the volume of a cube that is 10 centimeters (10 cm) along each edge (10 cm 10 cm 10 cm = 1000 cm3 = 1 L).

Units and QuantitiesUnits of Temperature

Scientists commonly use two equivalent units of temperature, the degree Celsius and the kelvin.

Units and Quantities

The joule (J) is the SI unit of energy. One calorie (cal) is the quantity of heat that raises the

temperature of 1 g of pure water by 1°C.

Section Quiz.1. Which of the following is not a base SI unit?

grammetersecondmole

Section Quiz.

3. A temperature of 30 degrees Celsius is equivalent to

303 K. 300 K. 243 K. 247 K.

THE END