Momentum

Solve these problems:

(33 x 106) + (3 x 104)

(4000 x 10-2) – (3 x 103)

Solve these problems:

(33 x 106) + (3 x 104)

Momentum

Solve these problems:

(33 x 106) + (3 x 104)

(3300 x 104) + (3 x 104)

Momentum

Solve these problems:

(3300 x 104) + (3 x 104)

3303 x 104

Momentum

Solve these problems:

(3300 x 104) + (3 x 104)

3303 x 104

3.303 x 107

Momentum

Solve these problems:

(4000 x 10-2) – (3 x 103)

Momentum

Solve these problems:

(4000 x 10-2) – (3 x 103)

(4000 x 10-2) – (300000 x 10-2)

Momentum

Solve these problems:

(4000 x 10-2) – (3 x 103)

(4000 x 10-2) – (300000 x 10-2)

-296000 x 10-2

Momentum

Solve these problems:

(4000 x 10-2) – (3 x 103)

(4000 x 10-2) – (300000 x 10-2)

-296000 x 10-2

-2.96 x 103

Momentum

5 Bonus Points(next week – 1 pt off everyday)Lab Fee, Safety Contract,

Notebook Set-up & Extra Item

Significant FiguresChap 1 pg.17

• Experimental work always has error!• Because of this it is important to minimize

error as much as possible when taking measurements

• Key Point #1 Accuracy is how close a measured value is to the true value

Accuracy Issues!

• Accuracy problems are always due to error– Method error – when measurements are

taken using two different methods• Ex. Reading a meniscus from different angles

– Instrument error – when measurements are taken using instrument that does not work correctly

• Ex. Balance is not calibrated or zeroed; worn down metersticks

• Key Point #2: Precision describes how exact a measurement can be. Typically due to limitations on the measuring instrument

Precision

• 1.345m is more precise than 1.3m– Ex. If meterstick is only divided into cm it will

be difficult to measure something a few mm thick

• A precise series of measurements will have values close to each other– 12.34kL; 12.35kL; 12.33kL = Precise– 12.343ng; 12.901ng; 22.392ng = NOT Precise

• Key Point #3: You can keep track of the precision of a measurement by using significant figures (sigfigs);

Significant Figures

-When you measure, Sig Figs are all the numbers you actually measure plus one estimated digit

-Ex. Measure this line with two different rulers…

Significant Figures-132.75g- 5 sigfigs- Actual measurement between 132.745g and 132.755g

Significant Figures

Significant Figures

Measurement Activity

Everyone should have rulers A, B & C…as well as

distance 1 & 2.

Significant Figures

Distance 1:Ruler A:Ruler B:Ruler C:

Significant Figures

Significant Figures

Distance 2:Ruler A:Ruler B:Ruler C:

Significant Figures

Key Point #4: There are 4 rules to counting sigfigs in

measurements!

Significant Figures

Significant Figures Rules#1 – All non-zero digits are significant!

Significant Figures

Significant Figures Rules

3462m

0031300kL

Significant Figures

Significant Figures Rules#2 – Zero Sandwich – zeroes between two non-zero digits are significant.(Ex. – 90003 has 5 sig figs)

Significant Figures

Significant Figures Rules

34062ms

00310300Gb

Significant Figures

Significant Figures Rules#3 – zeros at the end of a number and also to the right of the decimal are significant

Significant Figures

Significant Figures Rules

36200cW

03.130mHz

Significant Figures

Significant Figures Rules

306.200ph

0201500Ts

Significant Figures

Significant Figures Rules#4 – NO MATTER WHAT … zeroes to the left (of numbers) never count!!!

Significant Figures

0.0200ms100000000000000kJ

2028m

Significant Figures

100400g1.040kW9902.mW

Accuracy, Precision

• Is it possible for a set of data to be precise but not accurate? Explain.

Significant Figures

203.00000000.3

77.00

IP

The following students measure the density of a piece of lead three times. The density of lead is actually 11.34 g/cm3. Considering all of the results, which person’s results were accurate? Which were precise? Were any both accurate and precise?

a. Rachel: 11.32 g/cm3. 11.35 g/cm3. 11.33 g/cm3b. Daniel: 11.43 g/cm3, 11.33 g/cm3, 11.42 g/cm3c. Leah: 11.55 g/cm3, 11.34 g/cm3, 11.04 g/cm3

Exit TicketHow many significant digits in the following measurements?

702.0m.00340kL20700m

Organize the following measurements from the least accurate instrument to the most accurate.

98.020m 90m 18.23m