MEASUREMENT

Chapter One: Measurement

1.1 Measurements

1.2 Time and Distance

1.3 Converting Measurements

1.4 Working with Measurements

Section 1.1 Learning Goals

Define measurement.

Compare English and SI measurements.

Become familiar with metric prefixes.

Investigation 1A

Key Question: Are you able to use scientific tools to make

accurate measurements?

Measurement

1.1 Measurements

A measurement is a determination of the amount of something.

A measurement has two parts: a number value

and a unit

1.1 Two common systems

The English System is used for everyday measurements in the United States.

Miles, yards, feet, inches, pounds, pints, quarts, gallons, cups, and teaspoons are all English system units.

In 1960, the Metric System was revised and simplified, and a new name was adopted—International System of Units.

1.1 International System of Measurement (SI)

The acronym SI comes from the French name Le Système International d’Unités.

SI units form a base-10 or decimal system.

In the metric system, there are: 10 millimeters in a centimeter, 100 centimeters in a meter, and 1,000 meters in a kilometer.

1.1 The meter stick

A meter stick is 1 meter long and is divided into millimeters and centimeters.

1.1 The meter stickEach centimeter is divided into ten smaller units, called millimeters.

What is the length in cm?

Chapter One: Measurement

1.1 Measurements

1.2 Time and Distance

1.3 Converting Measurements

1.4 Working with Measurements

Section 1.2 Learning Goals

Explain the meaning of time in a scientific sense.

Discuss how distance is measured.

Use a metric ruler to measure distance.

1.2 Time and DistanceTwo ways to think

about time:

What time is it?

How much time?

A quantity of time is also called a time interval.

1.2 Time

Time comes in mixed units. Seconds are very short. For calculations, you may need to

convert hours and minutes into seconds.

How many seconds is this time interval?

1.2 Distance Distance is the

amount of space between two points.

Distance is measured in units of length.

The meter is a basic SI distance unit.

In 1791, a meter was defined as one ten-millionth of the distance from the North Pole to the equator. What standard is used today?

1.2 Metric prefixes Prefixes are added to the names of

basic SI units such as meter, liter and gram.

Prefixes describe very small or large measurements.

Chapter One: Measurement

1.1 Measurements

1.2 Time and Distance

1.3 Converting Measurements

1.4 Working with Measurements

Section 1.3 Learning Goals

Write conversion factors.

Apply the decimal point rule to convert between metric quantities.

Use dimensional analysis to convert English and SI measurements.

1.3 Converting unitsTo convert 1,565 pennies to the dollar amount, you divide 1,565 by 100 (since there are 100 pennies in a dollar).

Converting SI units is just as easy as converting pennies to dollars.

Convert 655 mm to m1. Looking for: …the distance in meters

2. Given: …distance = 655 millimeters

3. Relationships: Ex. There are 1000 millimeters in 1 meter

4. Solution:

655 mm = .655 meters

Solving Problems

Solving Problems

Convert 142 km to m1. Looking for: …the distance in meters

2. Given: …distance = 142 kilometers

3. Relationships: Ex. There are ? meters in 1 kilometer?

4. Solution: Use the conversion tool.

Solving Problems

Convert 754,000 cm to km1. Looking for: …the distance in kilometers

2. Given: …distance = 754,000 centimeters

3. Relationships: Ex. There are ? cm in 1 m? There are ? m in 1 km?

4. Solution: Use the conversion tool.

1.3 Converting units A conversion factor

is a ratio that has the value of one.

This method of converting units is called dimensional analysis.

To do the conversion you multiply 4.5 feet by a conversion factor.

Solving Problems

Convert 4.5 ft to cm1. Looking for: You are asked for the distance in cm

2. Given: You are given the distance in ft.

3. Relationships: Ex. There are ? cm in 1 ft? 30.48 cm = 1

ft4. Solution: Make a conversion factor from equivalent

1.3 Converting units Use the correct

conversion factor to convert:175 yds. to m.2.50 in. to mm.

Chapter One: Measurement

1.1 Measurements

1.2 Time and Distance

1.3 Converting Measurements

1.4 Working with Measurements

Section 1.4 Learning Goals

Determine the number of significant figures in measurements.

Distinguish accuracy, precision, and resolution.

Compare data sets to determine if they are significantly different.

Investigation 1B

Key Question: How can you use unit canceling to solve

conversion problems?

Conversion Chains

1.4 Working with Measurements Accuracy is how close a measurement

is to the accepted, true value. Precision describes how close

together repeated measurements or events are to one another.

1.4 Working with Measurements In the real world it is

impossible for everyone to arrive at the exact same true measurement as everyone else.

Find the length of theobject in centimeters. How many digits does your answer have?

1.4 Working with MeasurementsDigits that are always significant:

1. Non-zero digits.2. Zeroes between two significant digits.3. All final zeroes to the right of a

decimal point.Digits that are never significant:

4. Leading zeroes to the right of a decimal point. (0.002 cm has only one significant digit.)

5. Final zeroes in a number that does not have a decimal point.

Solving Problems

What is area of 8.5 in. x 11.0 in. paper?

1. Looking for: …area of the paper

2. Given: … width = 8.5 in; length = 11.0 in

3. Relationship: Area = W x L

4. Solution: 8.5 in x 11.0 in = 93.5 in2

# Sig. fig = 94 in2

1.4 Working with Measurements Using the bow

and arrow analogy explain how it is possible to be precise but inaccurate with a stopwatch, ruler or other tool.

1.4 Resolution

Resolution refers to the smallest interval that can be measured.

You can think of resolution as the “sharpness” of a measurement.

1.4 Significant differences In everyday conversation, “same”

means two numbers that are the same exactly, like 2.56 and 2.56.

When comparing scientific results “same” means “not significantly different”.

Significant differences are differences that are MUCH larger than the estimated error in the results.

1.4 Error and significance How can you tell if two results are

the same when both contain error (uncertainty)?

When we estimate error in a data set, we will assume the average is the exact value.

If the difference in the averages is at least three times larger than the average error, we say the difference is “significant”.

1.4 Error How you can you

tell if two results are the same when both contain error.Calculate errorAverage errorCompare

average error

Solving ProblemsIs there a significant difference in data?1. Looking for:

Significant difference between two data sets2. Given:

Table of data3. Relationships:

Estimate error, Average error, 3X average error4. Solution:

Math answer: 93.5 in2 Determine # of significant figures = 94 in2