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```markdown # 1.3 How Do We Measure Physical Quantities? **Precision of an Instrument** * The smallest unit an instrument can measure is known as its precision. * The precision of a metre rule and a measuring tape is $1mm$, hence the measurement is recorded to $1mm$. * To account for other m...

```markdown # 1.3 How Do We Measure Physical Quantities? **Precision of an Instrument** * The smallest unit an instrument can measure is known as its precision. * The precision of a metre rule and a measuring tape is $1mm$, hence the measurement is recorded to $1mm$. * To account for other more significant sources of error when using the digital calipers and digital micrometer screw gauges, we record the measurements shown on: * the digital calipers to $0.1mm$; and 1dp. eg. $147.21mm= 147.2 mm (1dp)$ * the digital micrometer screw gauge to $0.01mm$. **Question:** How will you measure the thickness of one sheet of your Physics Textbook? | Instrument | Measuring Range | Smallest Division | Example of Usage | | -------------------- | --------------- | ----------------- | -------------------- | | measuring tape | Zero to several meters | $0.1cm$ or $1mm$ | a person's waist | | metre rule | Zero to $1m$. | $0.1$ or $1mm$. | height of a table | | digital calipers | Zero to $15cm$. | $0.01cm$ or $0.01mm$ | diameter of a test tube | | digital micrometer screw gauge | Zero to $2.5cm$ | $0.001cm$ or $0.001$| diameter of a wire | # 1.3 How Do We Measure Physical Quantities? **Measurement of Time** * The SI unit for time is second $(s)$. * Measuring instruments include stopwatches, clocks & pendulums. * The instrument used to measure time will depend on the accuracy and precision needed. **Question:** Can you think of recurrent motions that can be used to measure time? # 1.3 How Do We Measure Physical Quantities? **Simple Pendulum** * A complete oscillation is the motion of a pendulum when it starts swinging from its starting point and ends its swing at its original starting point. (From $R \rightarrow S \rightarrow R$). The image shows three images of a pendulum swinging showing R at the start and finish and S at the midpoint.