http://www.ck12.org Chapter 1. What Is Science?
1.4 Measurement and Recording Data
Objectives
- Describe measurement.
- Explain what is meant by significant digits.
- Determine the number of significant digits in a measurement.
- Add, subtract, multiply, and divide with significant digits.
- Use scientific notation.
Vocabulary
- precision:The smallest unit that a device can measure.
- significant digits:The number of precisely-measured digits in a measurement or result.
- uncertainty (in measurement):The possible variance between a measurement and the true result.
How to Measure
A typical meter stick is accurate to a millimeter. Assuming the object being measured lines up well with the
meter stick and has a sharply-defined end, you can clearly see it measuring closer to one millimeter mark than to
another. This is expressed asprecisionof±0.5 mm, or equivalently,±0.05 cm. A measurement of 42.78 cm can
be read exactly to 42.7 cm (Figure1.6). The “8” in 42.78, that is, 0.08 cm, is a reasonable estimate, where the
actual measure lies within a range of values between 42.78±0.05 cm→[42.73 - 42.83]. This measurement has 4
significant digits.
FIGURE 1.
What reading wouldyouuse assign to the
position of the arrowhead?Introduction
A person stands on their bathroom scale. What is a reasonable weight for the scale to show?
A reasonable weight might be: