Drill

1
Drill

• Part 1- A single single unit conversion
• Convert 0.1 (or 10-1) m to ___ cm. Give answer
  in scientific notation.
• Part 2 - Draw 3 dart boards
• On one, show 6 darts that have accuracy (on
  average), but no precision
• On another, show 6 darts that have precision but
  no accuracy
• On the last, show 6 darts that have accuracy and
  precision.

2
Target analogy
Accuracy (on average) but no precision
3
Target analogy
Precision, but no accuracy
4
Target analogy
Accuracy Precision!
5
Extra credit assignmentdue Wednesday 9/27

• Make a cartoon poster for one safety rule.
• If it looks good enough to me, I will laminate it
  put it up in the classroom.
• It should be
• No dialogue, just pictures with the safety rule
  as a caption underneath
• Big enough to see from across the room
• Funny is good, but it needs to be clearly related
  to the safety rule.

6
Accuracy ? Precision!!!

• If there is accuracy ? does not necessarily mean
  there is precision.
• If there is precision ? does not necessarily mean
  there is accuracy.

7
Making precision quantitative

• Scientists speak in numbers a lot.
• 1 1.000 000 000?
• Not for scientists!
• Which number is more precise?
• So what?

8
Which would you prefer? Copy circle column A
or B.
B Salary 1000.00/wk Chemistry grade
96 3.000 grams chemotherapy drug 2.50 Bag of
chips mass 500.1 g

• A
• Salary 1,000/wk
• Chemistry grade A
• A few grams of chemotherapy drug
• 2 Bag of chips mass 500 g

9
Making precision quantitative

• When making a measurement, the data should only
  include meaningful numbers, based on how precise
  the machine is.
• Pour exactly 101 L several times into a graduated
  cylinder and read volume
• 100.1L, 101.2 L, 103.9 L,102.0 L
• Which numbers change? Which stay the same?
• Machine is precise only to tens place.

10
Significant Digits (Sig. Dig.)

• AKA Significant Figures (Sig. Fig.)
• Sig Fig of meaningful numbers plus 1st number
  that has uncertainty
• GC from last slide
• 100.1L, 101.2 L, 103.9 L,102.0 L
• 1st number of uncertainty is in singles place.
• So, when measuring a volume around 100 L in this
  GC, write down 3 or 3 Sig. Fig.
• 100 L, 101 L, 104 L,102 L

11
Class examples

• 4 meausurements

12
When you are reading other peoples numbers

• All non-zero numbers are significant
• All trailing zeroes are significant ONLY IF there
  is a decimal point
• All zeroes between no-zeroes are significant
• Place-holder zeroes are not significant.

13
(No Transcript)