Slide 1

Ms Ritcey Welcome to Physics 12 Slide 2 Plan: Course outline, expectations, about me, etc. Joke of the day/clip of the day Review: SF Precision Error Accuracy Slide 3 Joke of the day/clip of the day: Fans of the Big Bang Theory???? http://www.youtube.com/watch?v=JtL5q1IACfo Slide 4 Measurement When taking measurements, it is important to note that no measurement can be taken exactly Therefore, each measurement has an estimate contained in the measurement as the final digit When taking a measurement, the final digit is an estimate and an error estimate should be included Slide 5 Least Count When using a measuring device (non-digital) the least count should be determined The least count is the smallest division that appears on the device (i.e. for a metre stick, it would usually be mm) When taking a measurement, the digits should be recorded one place past the least count i.e. for a metre stick, a recording should be to tenths of mm Slide 6 Digital Devices Digital devices make the error estimate for you so you will simply record the digits presented on the device The device should also include an error estimate in the manual or on the label of the device Slide 7 Error Estimate The error estimate should be for the final digit in a measurement and is commonly 5 For a meter stick, a measurement would be recorded as 1.5743 .0005m Slide 8 Significant Figures Because all numbers in science are based upon a measurement, the estimates contained in the numbers must be accounted for Could 1+1=3? While conventional wisdom tells us this is not true, from a science standpoint it could be: 1.4+1.4=2.8 Slide 9 Significant Figures It is therefore important to know when a digit is significant A digit is significant if: It is non-zero (i.e. 4246 4SFs) A zero is between two non-zeros (i.e. 40003 5SFs) A zero is to the right of the decimal and to the right of a non-zero (i.e. 4.00 3SFs or 0.00210 3SFs) All digits in scientific notation (i.e. 3.57x10 3 3SFs) Slide 10 Significant Figures The rule that we will use for mathematical operations and significant figures is: Consider all values used in a calculation; the one with the fewest significant figures will determine the number of significant figures in your answer Slide 11 Page 942 (3, 4, 5a, 5b, 6) 3) 3, 2, 3, 2, 3, 1, 3, 7, 1, 2, 4, 4 4) 1.2, 2.3, 5.9, 6.9, 6.3, 4.5, 5.5, 10. 5) 9.7, 290 6) 2.5597x10 0, 1x10 3, 2.56x10 -1, 5.08x10 -5 Slide 12 Precision and Accuracy Precision describes the exactness and repeatability of a value or set of values. A set of data could be grouped very tightly, demonstrating good precision but not necessarily accuracy Accuracy describes the degree to which the result of an experiment or calculation approximates the true value. Slide 13 Precision and Accuracy Slide 14 Error Random Error Small variations due to randomly changing conditions Repeating trials will reduce but never eliminate Unbiased Affects precision Systematic Error Results from consistent bias in observation Repeating trials will not reduce Three types: natural, instrument calibration and personal Affects accuracy There are two types of error that need to be considered following data collection in an experiment. Slide 15 Error Analysis There are two main calculations that we will use to analyse error in an experiment Percent Deviation Measures accuracy Percent Difference Measures precision Slide 16 To do : Page 939 1-5