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