1/10/11
Post date: Jan 10, 2011 2:53:49 PM
Bell Ringer: Explain the difference between the measurements 1.00m and 1.0000m.
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
P.25: 14-15 for practice
Prefixes
Each prefix has a "multiplier" associated with it. In order to change a unit with a prefix to the base unit, simply replace the prefix with the multiplier
e.g. the multiplier for kilo is 10^3, so 143 kilometers is the same as 143 x 10^3 meters.
Add Page 17: 4-5 to the previous 3 problems.
The factor-label method for changing units
See page 10 of your lab manual
Effectively, we multiply a measurement by a carefully chosen form of "1" to change the units without changing the value of the measurement.
e.g. 25.4 cm ---> inches
25.4 cm x (1 inch / 2.54 cm) = 10 inches
Factor-label practice
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