1. Physics: It’s all around you…
What is Physics?

2. What is Physics?
Physics is the science concerned with the fundamental laws of the universe.
Deals with:
Matter
Energy
Space
Time
And all of their interactions

4. Why take Physics? You are continuing in science
You are interested in pursuing a career in the health sciences/medical sciences (nurse, doctor, kinesiology, pharmacist,…)
Engineering
Architect
Airline Pilot, Air traffic controller
Computer science
Space/astronomy
Optician/Optometry
Meteorology
Naval career
….even careers such as firefighter, police (forensics),

5. But Wait…………. We need to review your math skills 
Scientific notation
SI units
Significant Digits & Calculations
Error
We will be doing this over the next few days

6. Day 1: Scientific Notation
Extremely large and extremely small numbers are difficult to work with in common decimal notation
Scientific notation, or standard notation, expresses a number by writing it in the form: a x 10n
Expression
Common decimal notation
Scientific notation
124.5 million kilometres km
1.245 x km
154 thousand picometres pm
1.54 x 105 pm
602 sextillion molecules
molecules
6.02 x 1023 molecules

7. Scientific Notation
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Why? An easier way to write very large or very small numbers.
In scientific notation, the number is expressed by:
1. writing the correct number of significant digits with one non-zero digit to the left of the decimal point
2. multiplying the number by the appropriate power (+ or – ) of 10

8. = 2.394 x 103 **large numbers have positive exponents
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Example:
2394
= x 1000
= x **large numbers have positive exponents
0.067
= 6.7 x 0.01
= 6.7 x **small numbers have negative exponents,
Note: scientific notation also enables us to show the correct number of significant digits. As such, it may be necessary to use scientific notation in order to follow the rules for certainty (discussed later)

9. Using your calculator….
On many calculators, scientific notation is entered using a special key; labelled EXP or EE. This key includes “x 10” from the scientific notation; you need to enter only the exponent. For example, to enter
7.5 x press 7.5 EXP 4
3.6 x press EXP +/- 3

10. Practice
1. Express each of the following in scientific notation (to 2 sig. dig.)
A) 6 807 B) C) D) E) F)
G) 0.80
H) 68
Answers:
6.8 x 103
5.3 x 10-5
3.9 x 1010
8.1 x 10-7
7.0 x 10-2
4.0 x 1011
8.0 x 10-1
6.8 x 101

11. Practice 2. Express each of the following in common notation
A) 7 x 101
B) 5.2 x 103
C) 8.3 x 109
D) 10.1 x 10-2
E) x 103
F) x 10-3
G) 6.3 x 102
H) 35.0 x 10-3
Answers: 70
5 200
0.101
630

12. Investigation: Training on the Job
Problem: How long (in hours) will it take the toy train to travel across Canada from east to west?
Materials:
Metre stick -Small wind-up toy or hotwheels car timer
Procedure:
Measure as carefully as you can , in centimetres, how far the vehicle can travel in 5 seconds
Repeat step one two more times and then calculate the average.
Observations:
Trial
Distance (cm) 1 2 3
Average

13. Questions:
How far (in cm) did the train travel in 1 second?
How far (in km) did the train travel in 1 second?
How many km would it travel in 1 hour?
How long would it take (in days) to go across Canada from St. John’s in Newfoundland to Victoria in British Columbia? (highway distance) **7314 km **post your group’s answer to this question on the board
Do you think it would make any difference if the vehicle travelled from west to east or east to west?

14. Extra Practice
Worksheet/homework

15. Day 2. SI Units

16. International System of Units (SI)
Over hundreds of years, physicists (and other
scientists) have developed traditional ways (or
rules) of expressing their measurements. If we
can’t trust the measurements, we can put no
faith in reports of scientific research. As such,
the International System of Units (SI) is used
for scientific work throughout the world –
everyone accepts and uses the same rules, and
understands that there are limitations to the
rules.

17. SI
SI Rules
In the SI system all physical quantities can be expressed as some combination of fundamental units, called base units. (i.e., mol, m, kg, …..) . For example:
1N = 1 kg•m/s => unit for force
1 J = 1 kg•m2/s2 => unit for energy

18. SI SI Rules The SI convention includes both quantity and unit symbols.
Note: these are symbols (e.g., 60 km/h) and are not abbreviations (e.g., mi./hr/)
When converting units, the method most commonly used is multiplying by conversion factors, which are memorized or referenced (e.g., 1 m = 100 cm, 1 h = 60 min = 3600 s)
It is also important to pay close attention to the units, which are converted by multiplying by a conversion factor (e.g., 1 m/s = 3.5 km/h)

19. SI (handout)
Useful conversion factors!

20. copy
SI Units
It is easiest to keep track of your units if you use ratios/conversion factors to convert your units.
Example problems:
Convert 34.5 mm to m.
Convert 23.6 mm to km.
(HINT: You can avoid careless mistakes by first converting from mm into m, and then converting from m to km.)
3) Convert 5 km/h into m/s

21. SI Units Practice Convert 12.5 cm into mm
An athlete completed a 5-km race in 19.5 min. Convert this time into hours.
A train is travelling at 95 km/h. Convert 95 km/h into metres per second (m/s)

22. Investigation #2: Measuring Human Reaction Time
With only a metre stick??!!??

23. Stopwatches
- For a number of different applications it is necessary to know how quickly a person is able to react to some situation. - The first problem with trying to measure reaction time is that we must find a way to NOT have the reaction time of the measurer influence the measurement.

24. Yes we can!!
With only a common metre stick, a couple of friends, and some common items in the classroom it can be done.
By measuring the distance a metre stick falls before being caught, we can use a Physics formula to turn distance into time.
You likely haven’t seen this equation yet, but it is coming soon…

25. How does this work? A couple of conditions are needed :
One assumption is that the metre stick is released, not thrown.
The second assumption is that gravity remains constant (with a value of 9.8 m/s2)

26. So what is this equation you ask?
∆t is the time in seconds, given the metre stick falls a distance ∆d metres. Be careful with your units, or you will get some strange values!

27. Your task
- Develop a simple procedure that clearly shows how you would conduct this investigation to minimize uncertainty
- Collect data for several trials for each member of your team. Record in a clear, meaningful manner.
- Convert your measured values into time values using the formula you just saw.
- Calculate the average reaction time for each member of the group, and then calculate the average reaction time for the whole group.
- Determine the percent difference between the shortest and longest reaction times in the group.

28. And what will be handed in?
- It is hoped that next day you will be able to exchange labs with another team who will evaluate your procedure.
- Their results and evaluation will be added to your lab as an appendix (their evaluation can be left as rough copy)
- Your lab will include Purpose, Apparatus (sketch), Procedure, Observations, Analysis (including percent difference calculations), Discussion (comments from the other team should help you here) and Conclusion and an STSE (relating science to technology, society, and the environment) example of the significance of reaction times
- For this lab, you will be submitting a single lab for the team but individual STSE examples (due on Monday)

29. Day 3. Uncertainty and Significant Digits

30. Uncertainty in Measurements:
There are two types of quantities used in
science: exact values and measurements.
Exact values include defined quantities (1 m = 100cm) and counted values (5 beakers or 10 trials).
Measurements, however, are not exact because there is always some uncertainty or error associated with every measurement. Because of this, there is an international agreement about the correct way to record measurements

31. Significant Digits
The certainty of any measurement is communicated by the number of significant digits in the measurement.
In a measured or calculated value, significant digits are the digits that are known for certain and include the last digit that is estimated or uncertain.
There are a set of rules that can be used to determine whether or not a digit is significant (read pg of text)

32. Significant Digits Rules:
(on handout)
Rules:
All non-zero digits are significant: N has four significant digits
In a measurement with a decimal point, zeroes are placed before other digits are not significant: has two significant digits
Zeroes placed between other digits are always significant: 7003 has four significant digits
Zeroes placed after other digits behind a decimal are significant: km and kg each has four significant digits

33. Significant Digits In a calculation:
(on handout)
In a calculation:
When adding or subtracting measured quantities, the final answer should have no more than one estimated digit (the answer should be rounded off to the least number of decimals in the original measurement) **number of decimal places matter
When multiplying or dividing, the final answer should have the same number of significant digits as the original measurement with the least number of significant digits ** significant digits matter
**when doing long calculations, record all of the digits until the final answer is determined, and then round off the answer to the correct number of significant digits (ADD TO HANDOUT)

34. Significant Digits
Practice:

35. Significant digits

36. Precision
Measurements also depend on the precision of the measuring instruments used – the amount of information that the instrument provides
For example, cm is more precise than 2.86 cm
Precision is indicated by the number of decimal places in a measured or calculated value

37. Precision Rules for precision:
All measured quantities are expressed as precisely as possible. All digits shown are significant with any error or uncertainty in the last digit.
For example, in the measurement cm, the uncertainty lies with the digit 4

38. Precision
The precision of a measuring instrument depends on its degree of fineness and the size of the unit being used
For example, a ruler calibrated in millimetres is more precise than a ruler calibrated in centimetres

39. Precision
Any measurement that falls between the smallest divisions on the measurement instrument is an estimate. We should always try to read any instrument by estimating tenths of the smallest division.

40. Precision
4. The estimated digit is always shown when recording the measurement.
Eg. The 7 in the measurement 6.7 cm would be the estimated digit

41. Precision
5. Should the object fall right on a division mark, the estimated digit would be 0.

42. Precision

46. worksheet

47. Reaction Time Lab – Step 2
Today you are to have your PROCEDURE ready to be evaluated by another team.
When you get another team's procedure to evaluate you are to follow it PRECISELY to determine reaction times for each of the members of your team.
When you are completed, return the lab to the team along with ONE hand written page outlining your thoughts on their procedure and the results of your testing. (i.e. your teams reaction times.)

48. Day 4. Error

49. Error in Measurement
Many people believe that all measurements are reliable (consistant over many trials), precise (to as many decimal places as possible), and accurate (representing the actual value). But there are many things that can go wrong when measuring. For example:

50. Error in Measurement
There may be limitations that make the instrument or its use unreliable (inconsistent)
The investigator may make a mistake or fail to follow the correct techniques when reading the measurement to the available precision (number of decimal places)
The instrument may be faulty or inaccurate; a similar instrument may give different readings

51. What are three things you can do during an experiment to help eliminate errors?
To be sure that you have measured correctly, you should repeat your measurement at least three times
If your measurements appear to be reliable, calculate the mean and use that value
To be more precise about the accuracy, repeat the measurements with a different instrument

52. Two Types of Error
Random error results when an estimate is made to obtain the last digit for an measurement
The size of the random error is determined by the precision of the measuring instrument
For example, when measuring length with a measuring tape, it is necessary to estimate between the marks on the measuring tape
If these marks are 1 cm apart, the random error will be greater and the precision will be less than if the marks were 1 mm apart.
Such errors can be reduced by taking the average of several readings

53. Two Types of Error RANDOM ERROR
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RANDOM ERROR
Results when the last digit is estimated
Reduced by taking the average of several readings

54. Systemic Error
is associated with an inherent problem with the measuring system, such as the presence of an interfering substance, incorrect calibration, or room conditions.
For example, if a balance is not zeroed at the beginning, all measurements will have a systemic error; using a slightly worn metre stick will also introduce error
Such errors are reduced by adding or subtracting the known error or calibrating the instrument

55. Due to a problem with the measuring device
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SYSTEMIC ERROR
Due to a problem with the measuring device
Reduced by adding/subtracting the error or calibrating the device

56. Accuracy & Precision
In everday usage, “accuracy” and “precision” are used interchangeably to descibe how close a measurement is to a true value, but in science it is important to make a distinction between them

57. Accuracy & Precision Accuracy:
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Accuracy & Precision
Accuracy:
- Refers to how closely a measurement agrees with the accepted value of the object being measured
Precision:
Describes how it has been measurement
Depends on the precision of the measurement

58. Percentage Error
No matter how precise a measurement is, it still may not be accurate.
Percentage Error is the absolute value of the different between experimental and accepted values expressed as a percentage of the accepted value

59. Percentage Difference
Sometimes if two values of the same quantity are measured, it is useful to compare the precision of these values by calculating the percentage difference between them

60. Practice Worksheet – math skills
Determine the percent difference between the shortest and longest reaction times in your group

61. How to Write a Lab Report
handout
Remember: include in your conclusion: “Relating Science to Technology, Society, and the Environment (STSE)” - provide an example of the significance of reaction times