Chapter One: Measurement

1.2 Time and Distance

1.3 Converting Measurements

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.

What is your reaction time?Sit at a table and rest your arm on thetable, with your hand hanging off theedge. Have a friend dangle a metricruler just above your thumb and indexfinger. When your friend drops the ruler,catch it quickly between your thumband finger. Record the centimeter markwhere you caught the ruler. Do several trials and discuss.

Approximate reaction times are: 0.10 seconds for 5 cm0.14 s for 10 cm0.18 s for 15 cm0.20 s for 20 cm,0.23 s for 25 cm0.25 s for 30 cm.

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?

How many total seconds doesThis time interval represent? There are 60 seconds in a minute, so multiply 30minutes by 60 to get 1,800 seconds.There are 3,600 seconds in an hour,so multiply 2 hours by 3,600 to get 7,200 seconds. Add up all the seconds to get your answer: 45 + 1,800 + 7,200 = 9,045 seconds.

1.2 Distance Distance is the amount of space between two points or how far apart 2 objects are.

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. Today, a meter is defined more accurately as the distance that light travels in a

fraction of a second.

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.

X 1000

1/100

1/1000

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.