1. Measurements in Physics

2. Fundamental Units
The SI system (AKA the System International or the metric system
There are 7 fundamental units:
Meter (m)- measures distance
Kilogram (kg) – measures mass
Second (s) – measures time
Ampere (amp) –measures electric current
Kelvin (K) – measures temperature
Mole (mol) – measures chemical quantities
Candela (cd) – measures light intensity

3. Derived Units
Derived units are combinations of two or more fundamental units.
Examples of derived units:
Newton- Measures force
Hertz –Measures frequency
Joule – measures energy
Coulomb – measures charges
Volt – measures potential difference
Watt – measures power
Ohm – measures resistance

4. Why Use the SI Units?
Unlike our common measurements, the metric system is based on multiples (or powers of) 10.

5. Scientific Notation
The conversions and expression of measurement sin the metric system are made easy by Scientific Notation
The format is always: #.### x 10#
Note: The number before the decimal cannot be a zero, it must be a 1-9 digit!
Example 3.0x108
The power of the ten is referred to the magnitude of the number
Positive exponents are large numbers
Negative exponents are small numbers

6. Converting to and from Simply count decimals!
Q. Write in decimal notation: 3.6x1012
Since the power is positive, I know that the number has to get larger. The magnitude is 12, so I have to move the decimal 12 places to the right.

7. Con’t Write in decimal notation 4.36x10-11
Since the power is negative, I know that the number has to get smaller. The magnitude is 11, so I have to move the decimal 11 places to the left.

8. Con’t Write in scientific notation 300000000
Since this is a large number I know the power of ten will be positive. So I count the number of times I move the decimal over so that just one nonzero number is in front of it and make this number the positive power of ten.

9. Con’t Write in scientific notation: 0.00000000578
Since this is a small number, the magnitude of ten must be negative. So I count the number of places I move the decimal until one number is in front of it, and make this the negative power of ten.

10. Let’s Practice… Try- Your turn to practice
Tough- This is hard, but you can do it!

11. Significant figures
One benefit of scientific notation, is it allows numbers to represent only the significant figures.
To determine the number of significant figures:
Is the decimal point absent or present?

12. Let’s Practice… Teacher- Let me model to help you out.
Together- Volunteers?
Try- Your turn to practice.
Tough- This is hard, but you can do it!

13. Pre-Fixes
Instead of writing out the power of ten (like we just did), scientists often use prefixes on the base unit to establish the magnitude of the measurement.
The prefixes you need to know are listed on page 1 of your reference table.
These prefixes also signify the order of magnitude of a measurement (by looking at the notation on our chart)

14. Another word for “order of magnitude”

15. Converting Formats
To convert between scientific notation and prefixes:
Put the number in scientific notation
Find the power of ten from the notation on the chart
Rewrite the original number replacing the power of 10 (so the x10#) with the prefix.
Don’t forget to use the correct base units!
To convert between prefixes and scientific notation (or powers of 10)
Make sure your units have a prefix.
Find the prefix on the chart.
Rewrite the original number replacing the prefix with the power of 10 notation from the chart.
Don’t forget to use the base units (that no longer have the prefix)

16. Let’s Practice Q. Write in standard units: 19 KJ
The prefix we have is a K. Looking on the chart, the notation of K is x103, so I rewrite the 19, replace the K with x103 and put on my base unit of J. My answer is 19x103 J

17. Let’s Practice Q. Write with a prefix : 6.9 x 10-9 m
The notation we have is x 10-9 , and looking at the chart that is the “nano” prefix. So I rewrite the number 6.9 and preplace the power of ten with the symbol for nano so my answer is 6.9 nm.

18. Let’s Practice… Teacher- Let me do another one
Together- Let’s try one together
Try- Your turn to practice
Tough- This is hard, but you can do it!

19. Converting Between Prefixes
We can use the following chart:
Easy trick: The number of zeros correspond to the power of ten for the prefix!
Another hint: when your going from big to small prefixes multiply. When you go from small to big prefixes divide.

20. Convert Between Units Complete the following conversions
Teacher: 350 µg = _______ mg
Together: 20 km = _______ m
Try: 850 l = _______ ml
Try: 8 cm = _______ m
Try: 3 mg = _______ g
Tough: 3x108m = _____________km

21. Approximating Size
Now that you practiced measuring the metric system, you will often be asked to approximate the size of something.
Based on what you learned fill in the following chart to help you remember:
The measurement of…
Is approximately….
one shoulder to the opposite finger tip
100 m (remember this equals 1 m)
10-1 m
10 -2 m
100 m
1 kg
1 g
100 kg

22. Performing Operations
It is easy to perform mathematic operations as long as we can use our calculators!
Go over for each kind how to… take the sin, cos, or tan; take the inverse functions; to put into and out of sci notation; enter in numbers in notation

23. Math Review Can you successfully…? Solve for a specific variable
Perform exponent operations
Solving for the missing side of a right triangle
Find an angle in a right triangle
Find out by doing each section of the worksheet at the corresponding station. Once you are done, get your answers checked. Based on what you did incorrectly and your conversation with Miss Shea, fill out page 8 of your notes.
Notice: If you don’t have quality notes written for EACH section, you will receive a zero for today’s work!