LecturePLUS Timberlake 1

Chapter 1

Measurements

Problem Solving Using Conversion Factors and SF’s

2

Initial and Final Units

1. A person has a height of 2.0 meters. What is

that height in inches?

Initial (given) unit = m

Final (unknown)unit = ____?__

2) Blood has a density of 0.05 g/mL. If a person

lost 0.30 pints of blood at 18°C, how many

ounces of blood would that be?

Initial (given) = pints Final (unk) unit = ___

LecturePLUS Timberlake 3

How many minutes are in 2.5 hours?

Initial or Given unit

2.5 hr

Conversion Final or Unknown

factor unit

2.5 hr x 60 min = 150 min

1 hr

cancel Answer (2 SF)

LecturePLUS Timberlake 4

Learning Check

A rattlesnake is 2.44 m long. How long is the snake in cm?

1) 2440 cm

2) 244 cm

3) 24.4 cm

LecturePLUS Timberlake 5

Solution

A rattlesnake is 2.44 m long. How long is the snake in cm?

2) 244 cm

2.44 m x 100 cm = 244 cm

1 m

LecturePLUS Timberlake 6

Learning Check

How many seconds are in 1.4 days?

Unit plan: days hr min seconds

1.4 days x 24 hr x ?? = ? sec

1 day

LecturePLUS Timberlake 7

Solution CF2

Unit plan: days hr min seconds

2 SF Exact

1.4 day x 24 hr x 60 min x 60 sec

1 day 1 hr 1 min

= 1.2 x 105 sec

LecturePLUS Timberlake 8

Unit Check

What is wrong with the following setup?

1.4 day x 1 day x 60 min x 60 sec

24 hr 1 hr 1 min

LecturePLUS Timberlake 9

Unit Check

1.4 day x 1 day x 60 min x 60 sec

24 hr 1 hr 1 min

Units = day2/hr2 Not the final unit needed

LecturePLUS Timberlake 10

Learning Check An adult human has 4650 mL of blood. How many gallons of blood is that?

Unit plan: mL qt gallon

Equalities: 1 quart = 946 mL

1 gallon = 4 quarts

Your Setup:

LecturePLUS Timberlake 11

Solution

Unit plan: mL qt gallon

Setup:

4650 mL x 1 qt x 1 gal = 1.23 gal

946 mL 4 qt

3 SF 3 SF exact 3 SF

LecturePLUS Timberlake 12

Steps to Problem Solving

Read problem Identify data Write down a unit plan from the initial unit

to the desired unit Select conversion factors Change initial unit to desired unit Cancel units and check Do math on calculator Give an answer using significant figures

LecturePLUS Timberlake 13

Learning Check

If the ski pole is 3.0 feet in length, how long is the ski pole in mm?

LecturePLUS Timberlake 14

Solution

3.0 ft x 12 in x 2.54 cm x 10 mm = ? mm

1 ft 1 in. 1 cm

LecturePLUS Timberlake 15

Learning Check

If your pace on a treadmill is 65 meters per minute, how many seconds will it take for you to walk a distance of 8450 feet?

LecturePLUS Timberlake 16

Initial

8450 ft x 12 in. x 2.54 cm x 1 m

1 ft 1 in. 100 cm

x 1 min x 60 sec = 2400 sec

65 m 1 minfinal (2 SF)

Solution