1. Measurement in Physics

2. Warm-up Each definition will lead to a two-word, rhyming answer
Example: Mrs. Onassis’s tan pants
An introverted insect
Former President Clinton’s medicine
Blouse made of soil
Stupid Wrigley’s
A peculiar-looking goatee
An adorable apple or orange
An ailing baby bird
A flounder’s hope
An intelligent painting
Square container for smoked salmon

3. Why are we doing this?
This mini-unit will be used throughout the whole year and in every science class you take
Using proper/common SI units, scientific notation, sig figs, and error analysis allows scientists all over the world to communicate
It might seem overwhelming right now, but it will make more and more sense as the year progresses, practicing and using what we are discussing
We have already covered fundamental and derived SI units, metric conversions
Today we will discuss proper scientific notation, significant figures, and estimation
Next week we will cover the uncertainties inherent to all measurement

4. Scientific Notation
Allows us to easily use very large and very small numbers
Rules:
When adding or subtracting, the exponent MUST BE THE SAME
When multiplying and dividing the exponents do not have to be the same
A number in scientific notation is expressed as a x 10b, where a is a real number (called the coefficient) and b is an integer { … , -2, -1, 0, 1, 2, … }
·We say that the number is normalized if 1 ≤ |a| < 10

5. Scientific Notation
What would the following be written in scientific notation: 4,
53,000
6,720,000,000
0.2 2
Just be careful of significant figures!

6. Significant Figures From the head IB Physics grader/facilitator
“Significant digits and quantity units should be appreciated but will not be marked off if incorrect unless the question makes explicit reference to significant figures or quantity units.”
How I read this:
We need to discuss proper significant figures, but I will not make a huge deal out of it since IB doesn’t. Be logical and consistent when rounding decimal answers.
Example: Most of our measurement equipment can go no more than 2-3 decimals. Calculated answers from this data should do the same.

7. Significant Figures Rules Non-zero digits are always significant
345 (3 SF), (4 SF)
Zeros sandwiched between non-zero numbers are always significant
3405 (4 SF), (5 SF)
Non-sandwiched zeros to the left of a non-zero digit are not significant
0.345 (3 SF), (2 SF)
Filler zeros to the right of a decimal point are significant only if they are to the right of a non-zero digit
1.034 (4 SF), (5 SF), (1 SF), (4 SF)
Trailing zeros to the left of an implied decimal are not significant
300 (1 SF), 300. (3 SF)

8. Using Significant Figures
Multiplication and division – round your answer to the same number of significant digits as the quantity with the fewest number of significant digits.

9. Using Significant Figures
Addition and subtraction – round your answer to the same number of decimal places as the quantity with the fewest number of decimal places.

10. Orders of Magnitude and Estimation
These skills allow us to quickly check our work
Order of magnitude is only as accurate as the nearest power of 10
The mass of a human is around the order of magnitude 102
The speed of light is 3.00 x 108 ms-1. The order of magnitude is 108. It it were 9.00 x 108, a better order of magnitude estimation would be 109
Estimation is more precise than powers of 10
Whenever you use a non-digital instrument, there will always be an element of estimation
Estimation makes math easier, but less precise

11. Orders of Magnitude