Unit Conversions
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Transcript of Unit Conversions
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
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
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
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
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