Upcoming SlideShare
×

# Let’S Re Cap Sigfigs

476 views

Published on

Published in: Technology, Education
0 Likes
Statistics
Notes
• Full Name
Comment goes here.

Are you sure you want to Yes No
• Be the first to comment

• Be the first to like this

Views
Total views
476
On SlideShare
0
From Embeds
0
Number of Embeds
12
Actions
Shares
0
2
0
Likes
0
Embeds 0
No embeds

No notes for slide

### Let’S Re Cap Sigfigs

1. 1. Let’s Re-cap…
2. 2. <ul><li>In science, all numbers are based upon measurements (except for a very few that are defined). Since all measurements are uncertain, we must only use those numbers that are meaningful. A common ruler cannot measure something to be 22.4072643 cm long. Not all of the digits have meaning (significance) and, therefore, should not be written down. In science, only the numbers that have significance (derived from measurement) are written. </li></ul>
3. 3. <ul><li>All the significant figures in a measurement include: </li></ul><ul><ul><li>the known values </li></ul></ul><ul><li>a last digit that is estimated </li></ul><ul><li>Take a look at page 67, Figure 3.5 </li></ul><ul><li>To what decimal place would you measure using ruler: </li></ul><ul><ul><li>A? </li></ul></ul><ul><ul><li>B? </li></ul></ul><ul><ul><li>C? </li></ul></ul>
4. 4. <ul><li>All the significant figures in a measurement include: </li></ul><ul><ul><li>the known values </li></ul></ul><ul><ul><li>a last digit that is estimated </li></ul></ul><ul><li>A: </li></ul><ul><ul><li>What we know what we guess </li></ul></ul>
5. 5. <ul><li>All the significant figures in a measurement include: </li></ul><ul><ul><li>the known values </li></ul></ul><ul><ul><li>a last digit that is estimated </li></ul></ul><ul><li>B: </li></ul><ul><ul><li>What we know what we guess </li></ul></ul>
6. 6. <ul><li>All the significant figures in a measurement include: </li></ul><ul><ul><li>the known values </li></ul></ul><ul><ul><li>a last digit that is estimated </li></ul></ul><ul><li>C: </li></ul><ul><ul><li>What we know what we guess </li></ul></ul>
7. 7. Rules for determining if a digit in a measured value is significant: <ul><li>The book gives you a long drawn out explanation…boooo… </li></ul><ul><li>What we are going to use is the Atlantic Pacific Rule </li></ul>
8. 8. The Atlantic Pacific Rule <ul><li>If the decimal is present: </li></ul><ul><ul><li>Start on the pacific side (left) </li></ul></ul><ul><ul><li>Start counting with the first non-zero digit and keep counting to the right until you run out of digits </li></ul></ul><ul><li>If the decimal point is absent: </li></ul><ul><ul><li>Start on the atlantic side (right) </li></ul></ul><ul><ul><li>Start counting with the first non-zero digit and keep counting to the left until you run out of digits </li></ul></ul>
9. 9. On your own… <ul><li>Practice determining the correct number of sig figs using the handout I gave you yesterday. Raise your hand if you need one. Use the Pacific Atlantic Rule to help you. </li></ul><ul><li>When you are done that, I want you to round off each one of those numbers to two digits using scientific notation. </li></ul><ul><li>Ex: 452 4.5X10 2 </li></ul><ul><li>Ex: 2.081 2.1X10 3 </li></ul>
10. 10. Addition and Subtraction <ul><li>“A chain is only as strong as its weakest link.” </li></ul><ul><li>Addition/subtraction rule: </li></ul><ul><ul><li>The number of decimal places in your answer is determined by the measurement with the least number of decimal places. </li></ul></ul><ul><ul><li>Ex: 6.45 + 7.03 + 8.5 </li></ul></ul><ul><ul><li>Ex: 10 + 7.3 + 3.789 </li></ul></ul>
11. 11. Multiplication and Division <ul><li>The number of sig figs in your answer is determined by the measurement with the least number of sig figs. </li></ul><ul><li>Ex: 6.3 X 7.54 </li></ul><ul><li>Ex: ( 6.0 X 10 2 ) X 7.54 </li></ul>
12. 12. Try on your own: <ul><li>Questions 1-5 (both sets) </li></ul>
13. 13. Dimensional Analysis <ul><li>A way of solving problems using units of the measurements. </li></ul><ul><li>You already know how to do this… </li></ul><ul><li>How many seconds are in a year? </li></ul><ul><li>The unit changes, but the quantity doesn't </li></ul>
14. 14. Some conversion factors: <ul><li>1 inch = cm </li></ul><ul><li>12 inches = 1 foot </li></ul><ul><li>5,280 feet = 1 mile </li></ul><ul><li>1 foot = 0.3048 meters </li></ul><ul><li>1 kilogram = 2.2lbs </li></ul><ul><li>8 oz = 1 cup </li></ul><ul><li>2 cups = 1 pint </li></ul><ul><li>2 pints = 1 quart </li></ul>
15. 15. Dimensional Analysis <ul><li>Other useful conversion factors can be found listed in: </li></ul><ul><ul><li>Tables 3.2 – 3.4 (pgs 74-75) </li></ul></ul>
16. 16. Lets try some: <ul><li>A student is 6 ft. tall. What is this students height in meters? </li></ul>
17. 17. <ul><li>Boston and New York are 100 miles apart. What is this distance in meters? </li></ul>
18. 18. <ul><li>At the Indy 500, race cars typically travel around the track at an average speed of 225mph. What is this speed in km/h? </li></ul>
19. 19. Homework: <ul><li>Sig Figs Practice Sheet (Part I, Section B Worksheet – Complete Parts A and B) </li></ul>