Measurement (Cambridge (CIE) IGCSE Physics)

Measuring length & volume

• When making measurements in physics, different instruments are used for different measurements

Measuring length

• Rulers can be used to measure small distances of a few centimetres (cm).

  • They are able to measure to the nearest millimetre (mm)

A ruler can measure lengths in cm or mm

• A tape measure is used to measure lengths of tens of centimetres

• A trundle wheel is used to measure lengths of tens of metres

Trundle wheels can be used to measure larger distances

Measuring volume

• Measuring cylinder are used to measure the volume of liquids

  • By measuring the change in volume, a measuring cylinder can also be used to determine the volume of an irregular shape

Measuring cylinders can be used to determine the volume of a liquid or an irregular shaped solid

Measuring time

• In physics, stop-clocks and stopwatches are usually used to measure time intervals

• An important factor when measuring time intervals is human reaction time

  • The standard human reaction time for an alert person is 0.25 s 

  • This can have a significant impact upon measurements when the measurements involved are very short 

Multiple readings

• In physics, multiple readings of measurements are often taken to reduce the impact of measurement errors

Taking multiple measurements in physics

• The measurement of the thickness of a single sheet of paper is so small that it would be very difficult to get an accurate answer

  • However, measuring the thickness of 100 sheets of paper can be done much more accurately

  • Dividing the answer by 100 then gives an accurate figure for the average thickness of one sheet

• Measuring the time period of a simple pendulum would incur a human reaction time error at the start of the measurement and at the end of the measurement

• If the measurement is small, the uncertainty in the measurement is huge

• Therefore, multiple readings can be taken to reduce the uncertainty of the measurement

  • The time taken for 10 swings of the pendulum can be measured

  • Dividing the answer by 10 gives a more accurate figure for the average time taken for one swing