Momentum
Solve these problems:
(33 x
6
10 )
(4000 x
+ (3 x
-2
10 )
4
10 )
– (3 x
3
10 )
Momentum
Solve these problems:
(33 x
6
10 )
+ (3 x
4
10 )
Momentum
Solve these problems:
(33 x
6
10 )
(3300 x
+ (3 x
4
10 )
4
10 )
+ (3 x
4
10 )
Momentum
Solve these problems:
(3300 x
4
10 )
3303 x 104
+ (3 x
4
10 )
Momentum
Solve these problems:
(3300 x
4
10 )
3303 x 104
3.303 x
7
10
+ (3 x
4
10 )
Momentum
Solve these problems:
(4000 x
-2
10 )
– (3 x
3
10 )
Momentum
Solve these problems:
(4000 x
-2
10 )
– (3 x
3
10 )
(4000 x 10-2) – (300000 x 10-2)
Momentum
Solve these problems:
(4000 x
-2
10 )
– (3 x
3
10 )
(4000 x 10-2) – (300000 x 10-2)
-296000 x
-2
10
Momentum
Solve these problems:
(4000 x
-2
10 )
– (3 x
3
10 )
(4000 x 10-2) – (300000 x 10-2)
-296000 x
-2
10
-2.96 x 103
5 Bonus Points
(next week – 1 pt off everyday)
Lab Fee, Safety Contract,
Notebook Set-up &
Extra Item
Significant
Figures
Chap 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 nonzero 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
0.0200ms
100000000000000kJ
2028m
Significant Figures
100400g
1.040kW
9902.mW
Accuracy, Precision
• Is it possible for a set of data to be precise
but not accurate? Explain.
Significant Figures
203.0
0000000.3
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/cm3
b. Daniel: 11.43 g/cm3, 11.33 g/cm3, 11.42 g/cm3
c. Leah: 11.55 g/cm3, 11.34 g/cm3, 11.04 g/cm3
Exit Ticket
How many significant digits in the
following measurements?
702.0m
.00340kL
20700m
Organize the following measurements
from the least accurate instrument to the
most accurate.
98.020m
90m
18.23m