1. Measurement and Calculations

2. Murphy’s Law 0 Captain Edward A. Murphy Jr. was an engineer in the Air Force.engineerAir Force 0 In 1949, officers were conducting tests to determine once and for all how many Gs -- the force of gravity -- a human being could withstand.gravity 0 The project team used a rocket sled dubbed the "Gee Whiz" to simulate the force of an airplane crash.rocketcrash 0 The sled traveled more than 200 miles per hour down a half-mile track, coming to an abrupt stop in less than a second. 0 The the team needed an actual person to experience it. Enter Colonel John Paul Stapp.

3. 0 A set of sensors that could be applied to the harness that held Dr. Stapp to the rocket sled. These sensors were capable of measuring the exact amount of G-force applied when the rocket sled came to a sudden stop, making the data more reliable. 0 The first test after Murphy hooked up his sensors to the harness produced a reading of zero -- each one was installed the wrong way. 0 During his ride he was subjected to broken bones, concussions and broken blood vessels in his eyes all in the name of science. 0 So became Murphy’s Law.

4. What did we learn? 0 Having accurate calculations and measurements is essential in conducting experiments, especially when conducting experiments that could prove to be dangerous.

5. Certainty 0 When communicating in science you should express how certain you are about your measurements. 0 This Degree of Certainty(or uncertainty) is expressed as: record all those digits that are certain plus one uncertain digit, and no more. 0 These “certain-plus-one” digits are called significant digits. 0 The certainty of a measurement is determined by how many certain digits (plus one) are obtained by the measuring instrument.

6. The measurement of the distance from the centre of point A to the centre of point B is 2.05 cm. with a certainty of 3 significant digits.

7. 0 The greater the number of significant digits, the greater the certainty of the measurements. 0 Rule: All digits included in a stated value (except leading zeros) are significant digits. 0 The position of the decimal point is not important when counting significant digits; ignore the decimal point! 0 Ex: Adam has a vertical leap of 15.75 inches. This measurement contains 4 significant digits.

9. Certainty of Measurement Chart MeasurementCertainty 307.0 cm4 significant digits 61 m/s2 significant digits 0.03 m1 significant digits 0.5060 km4 significant digits 3.00 x 10³ m/s3 significant digits

10. Counted or Defined Values 0 When you directly count the pairs of shoes in your closet, this is an exact number. 0 When you find the average height in the class you can get an exact value. 0 Exact(counted) and defined values are thought to have an infinite number of significant digits. 0 Defined values include such examples as 100 cm/m and 60 s/min.

11. Exact Values Counted ValuesDefined Values 4 cars1000 m/km 60 DVDs10 mm/cm 9 snowballs1 h/ 60 min

12. Certainty Rule for Multiplying and Dividing

13. Rounding 0 To obtain the correct certainty we need a general rule for rounding answers. 0 Rule: If the digit after the digit to be retained as significant is a 5 or greater, round up. 0 Ex: Rounding 9.147 cm to three significant digits would yield 9.15 cm. 0 Rounding 7.23 g to two significant digits would yield 7.2 g.

14. Precision Rule for Adding and Subtracting 0 Precision is defined as the place value of the last digit obtained from a measurement or calculation. 0 Rule: When adding and subtracting measured values of known precision, the answer has the same number of decimal places as the measured value with the fewest decimal places. 0 Ex: When adding 1.2 mm, 3.05 mm and 7.60 mm the answer can be no more precise then the least precise value of 1.2 0 Therefore the answer (11.85 mm) is rounded to 11.9 mm.

15. Did you Know? 0 The first interplanetary spacecraft launched by the United States, Mariner 1, never reached its target, Venus, because of one missing hyphen in its software.

16. Conventions of Communication 0 The previous rules are generalizations, however, they provide a set of principles that allow the science community to communicate with each other without much confusion. 0 Despite these guidelines many people understand that their are limitations to these rules. 0 The scientific community agree to the SI conventions that include quantity and symbols. 0 Ex) km not mi (miles) and h not hr (hours)

17. Solving Equations

18. Converting Units