Unit Conversions Objective Convert between different SI units

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 signed Quiz tomorrow

0 1 2 3 4 5 6 7 8 24 H in a D 9 32 is the T in D F at which W F 10 5. T on a F 26 L of the A 7 D of the W 7 W of the W 12 S of the Z 90 D in a R A 52 C in a P (W J) 13 S in the U S F 18 H on a G C Conversion factors …in our lives

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 •

BIG IDEA #2 for Dimensional Analysis • • 4 x 1 = 4 10 x 1 = 10 yx 1=y BIG IDEA #2: any value multiplied by 1 has the same value

Example #1 •

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

Gradesheets • Grading Policy – Quizzes – 25% – Interim Assessments – 20% – Tests – 15% – Homework – 15% – Classwork – 10% – Labs & Projects – 10% – Participation – 5%