1. Measurement and Calculations
Physics 10
Measurement and Calculations

2. Certainty – when measuring, record all digits that are certain plus one uncertain digit (an educated guess)
These “certainty-plus-one” digits are called Significant Figures.

3. Counted and Defined Values – numbers with an infinite number of significant digits!
Examples:
Counted Values
15 students
3 dogs
25 DVDs
Defined Values
1.609 km = 1 mile
28.23 g = 1 oz
2.540 cm = 1 inch
1 kg = 1000 g
1 m = 100 cm

4. Determining the Number of Significant Figures/Digits:
RULE: All digits included in a stated value (except place-holding zeros) are significant digits

5. 1. If the number has a decimal, do not count leading zeros.
Examples:
  

6. 2. If the number doesn’t have a decimal, do not count ending zeros.
Example:
20  
201 

7. Question: What do we do if we want to express the number 20 as having 2 significant digits?
Answer: Scientists tend to use scientific notation so that it is NEVER confusing as to how many significant digits there are.
Example: 20 would be written as

8. Question: What do we do if we want to express the number 2 as having 2 significant digits?
Answer: Use a decimal and add in a zero
Example: 2 would be written as

9. ** Practice Questions **

10. Rounding Numbers to the Correct Sig Fig’s
1. Count out the amount you need
2. Round the last number based on the number directly following it (4 and under, do not round; 5 and up, round up)
** Practice Questions**

11. Multiplication and Division
Certainty Rule for
Multiplication and Division
RULE: When multiplying and/or dividing, the answer has the same number of sig fig’s as the measurement with the fewest number of sig figs
LEAST SIG FIG RULE!!!
(practice questions)

12. Adding and Subtracting
Precision Rule for
Adding and Subtracting
RULE: When adding or subtracting measured values of known precision, the answer has the same number of decimal places as the measured value with the fewest decimal places.
(practice questions)

13. Converting Units – Dimensional Analysis
RULE: Use conversion factors to eliminate by multiplication and division
(practice questions)