8/26/10
Post date: Aug 26, 2010 12:44:13 PM
Operations with significant digits
Addition or subtraction
Round to the same decimal as the least precise measurement
e.g. 1.2 + 3.41 + 12.02 = ?
1.2 is rounded to the tenths place, so answer must be rounded to tenths place
1.2+3.41+12.02+0.002=16.632, but rounded to the tenths is 16.6
Multiplication or Division
Answer has same number of sig digs as the measurement with the fewest sig digs
e.g. 3.0 x 14.125
3.0 has 2 sig digs, 14.125 has 5 sig digs, so answer must have 2 sig digs
3.0 x 14.125 = 42.375
round to 2 sig digs, so answer is 42
Do page 25: 14-17
Factor-label for speeds
Speeds are always measured in (distance units) / (time units) (such as miles / hour or meter / second)
To convert these, simply convert either the distance or the time unit, then the other one
Be careful to place units correctly in conversion fractions that that unwanted units cancel
Units in calculations
treat units just like variables during calculations
units can multiply together, be squared, divide out, etc.
Examples:
15 m / 5 sec = 3 m/sec
3 ft x 4 ft = 12 ft^2
25 N / 5 N = 5
Factor-label / sig dig extravaganza