Calculators and Errors.( Sept 15, 2009 )

Calculators
has functions that you can use to do this easily.
- EXP
- EE
- X10
Do not use the (^) on your calculator, it does not recognize the order of operations in all cases

Expressing Error
- fundamental part of science
3 reasons for error
1) Physical errors in the measuring device
2) ‘sloppy’ measuring
3) changing ambient conditions.
- error is taken to be half the smallest division on you measuring

Calculated Errors
2 different possibilities
absolute error
percentage error

Absolute Error
Measured value minus accepted value.
Absolute error – measured – accepted
Positive number means your over the accepted value
Negative number means your under the accepted value

Percent error
Most common
Percent error= absolute error/accepted value

%error= measured-accepted x100
Accepted
= observed – theoretical x100
Theoretical

Dimensional Analysis

Just like converting between currencies in chemistry it is usually necessary to convert between units.
- this process is called dimensional analysis
Steps
-only 4 steps
1. find a unit equality
2. find the convertion factors
3. apply convertion factors
4. cancel units

How many miles are there in a 20 Km?

120 Km = 75 M

1 mi = 1.6 Km Unit equality

1= 1 mi convertion
1.6 Km factor

(120 Km) (1 mi) use convertion factor
( 1.6 Km)
Cancel units

(Christine Yaco's blog entry)