Welcome to Physics!

Class Policies and Procedures

Lab Safety Contract

Marshmallow Challenge! As a team build the tallest free-standing structure 20 sticks spaghetti One meter of tape One meter of string One marshmallow Marshmallow on top 18 minutes!

Do you really know how to take accurate and precise measurements? Grab a ruler and measure the length of your writing utensil. Record your answer in your notes. Be nice and share the rulers 

How to take a measurement What is the smallest increment? What length do we know? What length do we estimate? 0.1 cm 5.3 cm 5.35 cm

Rules with Instruments Estimate one place past smallest calibration Can only measure with same precision as device 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

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 units Can you think of any examples?? Area Density Speed Weight

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? All non-zeroes Zeros in between non-zeroes Zeros to the right of non-zeroes if decimal included 234.560 (0 is significant) 234560 (0 is not significant)

Which are not significant? Zeros to the left of non-zeroes 0.000234 (0s are not significant) Zeros to the right of non-zeros, if there is no decimal 234000 (0s are not significant)

Practice How many significant digits are in the following: 2.34 2,340 234.0 0.000234 0.0002340 100,234 100,230.0

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

Conversions Review…..How many sig figs? 100 101 0.001 0.00100 How 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