Welcome to Physics!. Class Policies and Procedures.
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Transcript of Welcome to Physics!. Class Policies and Procedures.
Welcome to Physics!
Class Policies and Procedures
Lab Safety Contract
Marshmallow Challenge!
As a team build the tallest free-standing structure20 sticks spaghettiOne meter of tapeOne meter of stringOne marshmallow
Marshmallow on top 18 minutes!
MEASUREMENTS
Do you really know how to take accurate and precise measurements?
o Grab a ruler and measure the length of your
writing utensil.
o Record your answer in your notes.
o Be nice and share the rulers
HOW TO TAKE A MEASUREMENT
0.1 cm
5.3 cm
5.35 cm
What is the smallest increment? What length do we know?What length do we estimate?
RULES WITH INSTRUMENTSo Estimate one place past smallest
calibrationo Can only measure with same precision
as deviceo Which ruler is more precise? This one or
the one you used?
ARE YOU GOOD AT TEXTING?
Is there a correlation between the length and circumference of your thumb and your “fluency” in texting?
Measure and record the length and circumference of your dominant thumb
"I'm All Thumbs"
Easy to text?(yes or no)
Student NameGender
(M/F)Thumb Circumference
(cm)Thumb Length
(cm)
WHAT IS THE STANDARD OF MEASUREMENT FOR SCIENCE?
The Metric System – SI Units Related by powers of 10
ALL SCIENTISTS, WORLD WIDE, USE SAME MEASURMENT!
STANDARD SI BASE UNITS
Length?Mass?Time?Volume?
DERIVED UNITS
Combination of base unitsCan you think of any examples??
AreaDensitySpeedWeight
GOSH, DO WE HAVE TO SHOW UNITS?
No Naked numbers……the number is meaningless if you do not know how it was measured.
Example: My walking speed is 1m/s
DAY 2
WHICH NUMBERS ARE SIGNIFICANT?
o All non-zeroeso Zeros in between non-zeroeso Zeros to the right of non-zeroes if decimal
includedo 234.560 (0 is significant)o 234560 (0 is not significant)
WHICH ARE NOT SIGNIFICANT?
o Zeros to the left of non-zeroes
0.000234 (0s are not significant)
o Zeros to the right of non-zeros, if there is no decimal
234000 (0s are not significant)
PRACTICEHow many significant digits are in the
following:2.342,340234.00.0002340.0002340100,234100,230.0
MULTIPLICATION/DIVISION RULE
Answer should contain only as many SFs as the measurement with the fewest SFs
MULTIPLY
9.315m x 1.355m =
MULTIPLY
9.315m x 1.355m = 12.621825 m2
Express answer as 12.62 m2
CONVERSIONSHow do I convert between meters and kilometers? Or meters and centimeters?
Review…..How many sig figs?
100
101
0.001
0.00100
PREFIXES FOR BASE UNITS
Giga (G) 1,000,000,000 Mega (M) 1,000,000 Kilo(k) 1,000 Hecta (h) 100 Deca(d) 10 Base Deci(d) 0.1 Centi(c) 0.01 Milli(m) 0.001
KHDUDCM
Kids
Have
Died
Using
Dumb
Crummy
Metrics
IN CLASS EXAMPLES
Distance from sun to Mars is
227 800 000 000 m
What is this in kilometers?
OPENING ACTIVITY
1. Convert the following to the designated units.
260,000,000m to km
0.000000452s to ms
2. How many sig figs are in the following numbers?
260,000,000m
0.000000452s
OPENING ACTIVITY
1. Convert the following to scientific notation:
260,000,000m 2.6 x 108m
0.000000452s 4.52 x 10-7s
2. Convert the following to the designated units.
260,000,000mm to km 260km
0.000000452s to ms 0.000452ms
3. How many sig figs are in the following numbers?
260,000,000m 2
0.0000004520s 4
PRECISION VS. ACCURACY Precision refers to the smallest available unit of
measurement on a device
1 meter is not the same thing as 1.000000 meters
Accuracy describes how repeatable a measurement might be
A measurement could be precise (0.0001 meters), but not very accurate (0.0001 m, 0.2300 m, 0.0002 m, 0.0001 m)
Or, it could be accurate (1m, 1m, 1m, 1m), but not very precise
Significant Figures help reflect the precision of a measurement
SCIENTIFIC NOTATION We use scientific notation to simplify the format of very
large and very small numbers
When done properly, using scientific notation will not change the value of a number
We use exponents and powers of 10 w/ scientific notation
Format is always…
#.#........ x 10#
SCIENTIFIC NOTATION When simply changing one number from standard to
scientific notation, be sure to retain all significant figures
Example – 1,200,000 = 1.2 x 106
Example – 1,205,001 = 1.205001 x 106
Other times you may be asked to reduce the number of significant figures
Example – Express 1,205,001 with three sig. figs. = 1.21 x 106
Example – Express 1,296, 789, 005,231 with four sig. figs. = 1.297 x 1012
PRACTICE – CONVERT TO SCIENTIFIC NOTATION
1,200,000 m =
1,200 m =
89 s =
PRACTICE – CONVERT TO SCIENTIFIC NOTATION
1,200,000 m = 1.2 x 106 m
1,200 m = 1.2 x 103 m
89 s = 8.9 x 10 s
PRACTICE – CONVERT TO SCIENTIFIC NOTATION WITH THREE SIG. FIGS.
1,200,000 m =
1,200 m =
8989736 s =
PRACTICE – CONVERT TO SCIENTIFIC NOTATION WITH THREE SIG. FIGS.
1,200,000 m = 1.20 x 106 m
1,200 m = 1.20 x 103 m
8989736 s = 8.99 x 106 s