Journal #2 8/16/10 Solve for x if

Solve for x if

2x 4 8

x3

4 8

Math and Graphing Notes

Chapter 1

Precision The precision of a number describes

the degree of exactness of the measurement. Ex. A beaker of water is placed on a

triple beam balance and is measured to have a mass of 421.5 grams. The same beaker is placed on an electronic balance and the mass is given as 421.5211 grams. Both numbers are correct, but the second number is more precise.

Accuracy For a measurement to be accurate,

the value must be very close to the “real” value. Ex. The teacher has already measured

the mass of a wooden block to be 11.2 grams. If a student were to measure the same block and return a mass of 11.3 grams, we would say that the student had a very accurate measurement.

Accuracy vs. Precision

Significant Figures All measurements that are made are

subject to some uncertainty. Some scales that you weigh objects on

might read to 1 decimal place while others might be more precise and measure to 3 decimal places

When doing math with measurements, numbers cannot become more precise.

Determining Sig Figs When given any number, there are

rules that can be followed to determine how many digits within that number are “precision” digits, aka Sig Figs.

Determining Sig Figs Let’s look a few examples:

a. 1492b. 101c. 200d. 0.005e. 0.750f. 102.070

Determining Sig Figs We will work through all 5 rules The first rule is the easiest…

All numbers that are non-zero numbers are ALWAYS sig figs.

When you first start counting Sig Figs, you may want to underline digits that are significant to help you.

Determining Sig Figs Underline the non-zero digits:

a. 1492 (all of these are sig figs)b. 101 (both of the 1’s)c. 200 (only the 2)d. 0.005 (only the 5)e. 0.750 (only the 7 and the 5)f. 102.070 (only the 1, 2, and 7)

Determining Sig Figs The only numbers remaining now are

zeros. The last 4 rules are called the zero rules.

Zero Rule #1 is easier to remember as the “sandwich rule”. If a zero is anywhere between two sig

figs, it is also a sig fig.

Determining Sig Figs Underline the sandwich zeros:

a. 1492b. 101 (yes)c. 200 (no sandwich)d. 0.005 (no sandwich)e. 0.750 (no sandwich)f. 102.070 (only the first and second 0)

Determining Sig Figs Zero Rule #2 is also called the

“trailing zero” rule Zeros that fall behind a sig fig but are in

front of the understood decimal point are NOT sig figs.

Determining Sig Figs Look for any trailing zeros:

a. 1492b. 101c. 200 (yes… both trail, so not sig figs)d. 0.005 (no, but the zero in front of the

decimal is obviously not a sig fig)e. 0.750 (no)f. 102.070 (no)

Determining Sig Figs Zero Rule #3 is also called the

“leading zero” rule Zeros that fall behind the decimal but

are in front of a sig fig are NOT sig figs.

Determining Sig Figs Look for any leading zeros:

a. 1492b. 101c. 200d. 0.005 (yes, the two zeros in front of

the 5 are leading zeros and are not sig figs)

e. 0.750 (no)f. 102.070 (no)

Determining Sig Figs Zero Rule #4 is also called the

“precision” rule Zeros that fall behind the decimal AND

are behind a sig fig are sig figs.

Determining Sig Figs Underline any precision zeros:

a. 1492b. 101c. 200d. 0.005e. 0.750 (yes, the last 0)f. 102.070 (yes, the last 0)

Determining Sig Figs Final Count:

a. 1492 (4 sig figs)b. 101 (3 sig figs)c. 200 (1 sig fig)d. 0.005 (1 sig fig)e. 0.750 (3 sig figs)f. 102.070 (6 sig figs)

Things to remember… Once you call a number a sig fig, you

can’t undo it by a later rule. Always follow the rules in order as

you determine sig figs. There may be times where you have

recheck the sandwich rule at the end. Example: 50.00

Journal #3 8/16/10 Determine the number of sig figs:

a. 10.70b. 10200c. 0.033d. 2.000e. 1350f. 0.0050

Journal #3 8/14/09 Determine the number of sig figs:

a. 10.70 (sandwich and precision)b. 10200 (sandwich)c. 0.033 (leading zeros don’t count)d. 2.000 (precision)e. 1350 (trailing zero doesn’t count)f. 0.0050 (precision zero only)

Scientific Notation Many times in science we have to use

very large numbers or very small numbers. In these times, it makes more sense to use a special notation rather than writing a number like 9,000,000,000,000 (same as 9x1012)

When using Scientific Notation, you must know how to count sig figs.

Scientific Notation Luckily, most calculators can do this

for you. But… in the event that you forget your calculator, everyone should know how to do this by hand.

After we review the “old-fashioned way”, I will demonstrate how to do this on the calculator.

Scientific Notation Please copy down these 3 example

numbers.a. 2603000b. 0.0000484c. 300000000

Please follow the rules and underline the sig figs in each number.

Scientific Notation Check your sig figs:

a. 2603000b. 0.0000484c. 300000000

Next, locate the decimal point in each number. If you don’t see a decimal point, it is understood to be at the far right (draw one in).

Scientific Notation Check your decimal points:

a. 2603000.b. 0.0000484c. 300000000.

To convert, you simply count the number of “places” that you will move the decimal until it lands behind the sig fig farthest to the left.

Scientific Notation Check your decimal points:

a. 2603000. (6 places)b. 0.0000484 (5 places)c. 300000000. (8 places)

Scientific Notation The number of places will become the

exponent on the power of ten (10n) If you move left the power is positive,

and if you move right the power is negative… just like on a number line.

Scientific Notation All you have to do now is write the

number (dropping all digits but the sig figs) and add on the power of ten.

For example A 2603000. becomes 2.603 x 106

Try doing the other two

Scientific Notation Check your answers:

b. 0.0000484 = 4.84 x 10-5

c. 300000000. = 3 x 108

Scientific Notation Now, the easy way… Find a button on your calculator with

the letters SCI (may be above a button or by pressing “mode”)

Select SCI to place your calculator in Scientific mode

Type any of our three examples and press enter.

Scientific Notation So a calculator can tell you the

scientific notation for any number… GREAT!

But what if I give you a question where the numbers are already in scientific notation and you have to use them mathematically…

How do you type them on the calculator?

Scientific Notation Copy down the following question:

(3.00 x 108) x (4.80 x 102) = ?

Before we go on, locate one of the following buttons on your calculator:

EE, x10n, or EXP

Scientific NotationEE, x10n, or EXP

These buttons allow you to enter a number that is already in scientific notation.

To enter the first number, press this:( 3.00 EE 8 )

You will probably see that the calculator screen only shows one E… that’s ok… don’t press it twice!

Scientific NotationEE, x10n, or EXP

To continue the problem, press this:x (4.80 EE 2) =

Your calculator will generate the answer for you and most likely give that answer in scientific notation.

Please wait for everyone to catch up.

Scientific Notation Check your answer:

(3.00x108) x (4.80x102) =? 1.44x1011

Raise your hand if you didn’t get this answer.

About your final answer… Now comes the reason we have done

all of this… In science, you are never allowed to

give a more precise answer than the measurements you started with.

The rule is that you must have the same number of sig figs in your answer as the LEAST amount in any number used in the problem.

About your final answer… In this case, 1.44x1011, has the same

number of sig figs as both of the beginning numbers (3). So no extra work is required. If you were to end up with less sig figs

than required, you would simply add on precision zeros.

If you were to end up with more sig figs than required, you would round the number.

Examples: Make each of the following numbers

have 3 sig figs: 2.758 x 10-8 5.1 x 104

Check with your neighbor

Examples: Check your answers:

2.758 x 10-8 rounds up to 2.76 x 10-8

5.1 x 104 adds a precision zero to become 5.10 x 104

Journal #4 8/16/10 Calculate the answer, remember to

use the correct sig figs in your answer:

(3.61108)(4.1108)

Journal #4 8/17/09 Your answer must only have 2 sig figs

(3.61108)(4.1108)

1.48011017

1.51017

Dimensional Analysis In the metric system, prefixes are

used on units to indicate the power of 10. You are expected to be able to convert between these without hesitation. (blanks are important, but you don’t need to know what goes there)

G _ _ M _ _ k h da _ d c m _ _ μ _ _ n

G _ _ M _ _ k h da _ d c m _ _ μ _ _ nSymbol Prefix Power of 10

G giga- 109

M mega- 106

k kilo- 103

h hepto- 102

da deca- 101

d deci- 10-1

c centi- 10-2

m milli- 10-3

μ (mew) micro- 10-6

n nano- 10-9

Dimensional Analysis Convert the following numbers:a) 3.75km = ______ mb) 0.003m = _______ mmc) 750g = _______ kgd) 2490mL = ______ Le) 0.0890kg = ______ cg

Dimensional Analysis Convert the following numbers:

a) 3.75km = 3750m (3 spaces right)b) 0.003m = 3mm (3 spaces right)c) 750g = 0.75kg (3 spaces left)d) 2490mL = 2.49L (3 spaces left)e) 0.0890kg = 8.90x103cg (5 spaces right,

but 3 sig figs)

Journal #5 8/18/09 Describe how confident you are about

the different parts of the quiz.

After the quiz, open your journal and write about how you feel you did.

Journal #6 8/19/09 About how far

had the ball fallen at 0.8s?

How long did it take for the ball to fall 12m? ?

?

Parts of a line graph: Title Axis Labels Number Scale Data Points Line Legend/Key

Title of Graph Placed above the top portion of the

graph Should be descriptive of what is being

observed Not necessary to use the word

“graph” in the title

Axis Labels Should have the independent variable

on the x-axis and the dependent variable on the y-axis.

Both Labels should also include the unit of measurement in parentheses

Number Scale Should be a pattern (counting by 2, 5,

10, etc) Should allow the graph to take up as

much space as possible on the available graph paper.

The scale usually starts at zero in the bottom left corner

Data Points Should be large enough to see, but

not much larger than the thickness of the line.

Placement must be very close to actual location for full credit.

Line Unless instructed otherwise, the

points should be connected from left to right (one at a time) using a ruler to make perfectly straight lines.

If there are multiple lines on a single graph, each line should have a different color to help distinguish it

Legend/Key A legend is only necessary if there are

multiple sets of data put on a single graph.

The legend should identify the data set and match it to the corresponding color used on the graph.

The usual placement for a legend is either to the right of the graph or below it.

Journal #7 8/20/09Speed (m/s) Stopping

Distance (m)11.0 18.016.0 32.020.0 49.025.0 68.029.0 92.0

Journal #7 8/20/09Speed (m/s) Stopping

Distance (m)11.0 18.016.0 32.020.0 49.025.0 68.029.0 92.0

Stopping Distance vs. Speed

Journal #8 8/21/09 Copy the following measurements:

3.09m 3.078m 3.40m

Which number is the most precise? If the actual value was supposed to

be 3.15m, which number is most accurate?

Part 6 and 7