Unit Conversions

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Unit Conversions

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Unit Conversions. Objective. Convert between different SI units Convert English units to SI units. Real World Example. Mars climate orbiter in 1999 Engineers at Lockheed Martin using US system for units Engineers at NASA using SI system for units - PowerPoint PPT Presentation

Transcript of Unit Conversions

Unit Conversions

Objective

• Convert between different SI units• Convert English units to SI units

Real World Example

• Mars climate orbiter in 1999• Engineers at Lockheed Martin using US system

for units• Engineers at NASA using SI system for units

Led to explosion of the Mars orbiter and loss of $125 million

Agenda

• Do Now• Heart of the Lesson #1 – Dimensional Analysis• Summary

• HW: 1.11 HW Dimensional Analysis + review questions

Get gradesheet signedQuiz tomorrow

Conversion factors…in our lives

0 24 H in a D1 26 L of the A

2 7 D of the W

3 7 W of the W

4 12 S of the Z

5 90 D in a R A

6 52 C in a P (W J)

7 13 S in the U S F

8 18 H on a G C

9 32 is the T in D F at which W F

10 5. T on a F

Conversion Factor:

• Factor equal to 1• Use it to convert from one unit to another

Dimensional Analysis:

• Problem-solving method that uses conversion factors to convert between units

• Not changing the value of the measurement, only the units

BIG IDEA #1 for Dimensional Analysis

• 4/4 = 1• 10/10 = 1• x/x = 1• BIG IDEA #1: any value divided by itself = 1

Example

24 hours = 1 day= = 1

The conversion factor is equal to 1 (any value divided by itself = 1)

BIG IDEA #2 for Dimensional Analysis

• 4 x1 = 4• 10 x 1 = 10• y x 1 = y • BIG IDEA #2: any value multiplied by 1 has the

same value

Example #1

How many centimeters are in 1 meter?100

Definition of a centimeter: 1 cm = 10-2 mConversion factor: 102 cm = 1 m

100 cm = 1 meter

How many centimeters are in 3 meters?

• Are centimeters bigger or smaller than meters?Smaller

• For any number of meters, I will have more centimeters

• So in 3 meters, will I have more or less than 3 centimeters?

More

• For any number of meters, I will have more centimeters

• Since I want the final number to be bigger, I have to multiply the original measurement by the conversion factor

Conversion factor:

Multiply orig. measurement by the conversion factor:

3 m x

3 m x 3 m x

3 x 100 cm = 300 cm

There are 300 cm in 3 meters

Example #2: How many hours are equivalent to 250 seconds?

Conversion factors: 60 min = 1 hr 60 sec = 1 min

• Are hours bigger or smaller than seconds?Bigger

For any number of seconds, I will have fewer hours• Since I want the final number to be smaller, I

have to divide the original measurement by the conversion factor

Divide by the conversion factors: and

250 s x x

250 s x x 250 s x x

hr= .0694 hr

There are .0694 hours in 250 seconds

Summary

• If you want the final answer to be bigger, you multiply by the conversion factor

• If you want the final answer to be smaller, you divide by the conversion factor

• The value is the same, but the units change• Conversion factor is what you use to convert

from one unit to another• Dimensional analysis is a way to convert btwn 2

diff units

Gradesheets

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