1. St. Augustine Preparatory School August 7, 2015
Physics
St. Augustine Preparatory School
August 7, 2015

2. Recap Convert the following: 1125 meters in kilometers
114 centimeters in meters
525.3 grams in kilograms
10.23 kilograms in grams

3. Significant Figures
Significant figures (also called significant digits) are important as they indicate the precision of a measurement
Page 18 in your textbook has the rules for determining the amount of significant figures in a number

4. Practice 1.0303 m h) 1000 kg 2.50 kg i) 6.723 m 0.00032 s j) 4.200 J
3.0x102 mm
45 s
40 s km

5. Rules for addition and subtraction
When adding and subtracting numbers, the final answer will have the same number of decimal places as the number used in the addition/subtraction that had the least number of decimal places.
Examples: =
125 – 5.5 =

6. Rules for multiplication and division
When multiplying and dividing, the final answer must have the same number of significant figures as the number used that had the least number of significant digits.
Examples:
24.0 x 1.5 =
36.00/2.00 =

7. Practice 97.3 + 5.85 = 122.3 – 0.52 = (124.2)(2.1) = (2x102)(1.232) =
24.56 / =
2.02x x105 = =
(1.20)(2.212)(0.0035) =

8. Why have we done all this?
Physics involves the use of a lot of different equations to describe relationships.
For example:
Velocity = (distance)(time)
Force = (mass)(acceleration)

9. Using units to solve problems
Even without knowing a formula, you can solve many physics problems just by looking at units
Ex. A car is travelling at a constant velocity of 88km/h. What amount of time will it take to travel 705km?

10. Practice Problems
McDonald’s sells approximately 75 hamburgers every second worldwide. How many hamburgers does McDonald’s sell in 3 minutes?
In the USA there is an estimated 121 million cars on the road. If the average car travels 16100km in a year and uses 9.00 liters of gasoline every 1.00x102km, what quantity of gasoline is used annually in the USA.

11. Units for Answers
The units (and significant figures) that we use for our answer must stay consistent with what was used to find the answer.
Ex. 1) 11m m + 13m = _____________
Ex 2) m / 1.3 s = ____________
Ex 3) (13.3 s)(2.0 s) = _____________
Ex 4) 1.5 s / 0.50 s = ____________

12. Accuracy and Precision
Accuracy: How close to the actual value a measurement is
Precision: How close together two or more measurements are to each other.
You can be precise, without being accurate!

13. Consider the game of darts, if a person is aiming at the center of the board.

14. Chapter Review Questions
Page 28: 13 – 16, 18, 20, 21, Page 30: 37, 38, 44