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