1. Accuracy Precision Sig Figs Graphing
Tools of Physics
Accuracy
Precision
Sig Figs
Graphing

2. Ruler (metric) (Overview)
Used to measure length/distance
Units of measure: centimeters (cm), millimeters (mm)
Markings
Each small (unnumbered) line is a millimeter division
Each long line followed by a number is a centimeter division
10 millimeters in a centimeter
1 mm
1 cm
Important – this is only a portion of a ruler

3. Ruler (How to Use)
Choose an object to measure and place it on a flat surface.
Align the ruler to the side of the object with the beginning of the object at the zero mark. Be careful, some rulers have the zero mark at the starting edge and some have a zero mark slightly indented.
Locate the opposite edge of the object and read the last number on the ruler where the object ends.

4. Ruler (metric) (Example)
What is the length (millimeters and centimeters) of the object below?
37 mm
3.7 cm
What is the relationship between your two answers?

5. Meter Stick (Overview)
Used to measure length/distance
Units of measure: meter (m), centimeter (cm), millimeter (mm)
Markings
Each small (unnumbered) line is a millimeter division
Each long line followed by a number is a centimeter division
10 millimeters in a centimeter
100 centimeters in a meter
How many millimeters are in a meter?
1 mm
1 cm
Important – this is only a portion of a meter stick

6. Meter Stick (How to Use)
Choose an object to measure and place it on a flat surface.
Align the meter stick to the side of the object with the beginning of the object at the zero mark. Be careful, some meter sticks have the zero mark at the starting edge and some have a zero mark slightly indented.
Locate the opposite edge of the object and read the last number on the meter stick where the object ends.

7. Meter Stick (Example)
What is the length (in meters, centimeters, and millimeters) of the object below?
0.246 m
24.6 cm
246 mm

8. Stopwatch (Overview) Used to measure time
Units of measure: seconds (s), minutes (min)
Buttons
Split/Reset:
Mode:
Start/Stop

9. Stopwatch (How to Use)
Reset the stopwatch by pressing the Split/Reset button on the top.
When you are ready to begin tracking time, press the Start/Stop button on the top.
When you are ready to stop tracking time, press the Start/Stop button again.

10. Stopwatch (Example)
What amount of time has elapsed?
12.6 seconds

11. Stopwatch (Example) What amount of time has elapsed?
1 minute, seconds

12. Significant Figures (Sig Figs)
What are significant figures? They’re sort of the "interesting" or "important" digits of a number. They indicate the precision of a measurement
Rules:
All nonzero numbers are significant (8762)
Leading zeros are never significant (0.035)
Imbedded zeros are always significant (2005)
Trailing zeros are significant only if the decimal point is specified (400 vs. 400.)

13. Precision vs. Accuracy
Accuracy: the closeness of a measured value to a standard or known value.
For example, if in lab you obtain a weight measurement of 3.2 kg for a given substance, but the actual or known weight is 10 kg, then your measurement is not accurate.
In this case, your measurement is not close to the known value and therefore, not accurate

14. Precision vs. Accuracy
Precision: the closeness of two or more measurements to each other
If you weigh a given substance five times, and get 3.2 kg each time, then your measurement is very precise.
Precision is independent of accuracy.
You can be very precise but inaccurate. You can also be accurate but imprecise.

15. Precision vs. Accuracy

17. Recording Measurements
When recording a measurement, include all of the known digits plus a final estimated digit.  
For example, in the ruler below it is marked every one centimeter so we know the ones place and could record 2.
But we must also estimate one, and only one, additional digit.  
So in this case we might record 2.3 cm or perhaps 2.4 cm.
Either would be correct as the 2 (ones place) is precisely known while the final digit (tenths place) is estimated.

18. Recording Measurements
When recording a measurement, include all of the known digits plus a final estimated digit.  
Now consider the next ruler.  In this case, the ruler is marked in both ones and tenths meaning that we can clearly see the first part of the measurement is 2.3. However, we must again estimate one additional digit or place – 2.35 cm.

19. Graphing Distance vs. Time
Time will be on the x-axis because it is the independent variable
Distance will be on the y-axis because it is the dependent variable (the distance traveled depends on the amount of time)

20. Graphing Distance vs. Time

21. Practice
What does this measure? Make sure you estimate one digit beyond what is known
How many significant figures?
5693
5900
4006
3400.

22. Practice Graph the following data: Label each axis and title the graph
Distance (m)
Time (s)
Trial 1 3 1
Trial 2 5 2
Trial 3 6 4
Trial 4
Trial 5 9