1/28/09

Post date: Jan 27, 2009 4:41:55 PM

• • Scientific notation ONLY shows sig digs (eliminates 0 confusion)

    • e.g. 251.30 --> 2.5130 x 10^2

    • e.g. 1001 --> 1.001 x 10^3

    • e.g. 0.00240 --> 2.4 x 10^-3

  • For the problems you did earlier, write each number in scientific notation

  • 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=16.63, 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

  • Units in Equations

    • Units in equations are treated just like variables

      • Can be multiplied or divided to create new units (e.g. miles / hours = miles per hour)

      • Can have exponents

      • Can be in numerator or denominator

  • Factor-label method of changing units

    • Effectively, we are multiplying by 1 in a carefully chosen format to change the unit without changing the value of the measurement

    • For detailed instructions, check out the file "Factor Label Method" in the file cabinet.

    • Convert the following measurements to the units indicated

      • 15 km to cm

      • 1.3 miles to inches

      • 4 weeks to minutes

      • 12 inches to cm

      • 15 feet to meters

      • The distance from your elbow to your wrist from inches to meters (check this)

      • The length of our class in minutes to years

      • Estimate how many years you will spend sleeping in your lifetime