CSEC Physics • Lesson 3 of 4Measurement Instruments, Error & Density · Myers Science Hub Student Centre
CourseCSEC Physics
Practice formatMCQ • Structured • Experimental
Your progress0% complete
Learning objectives
- Use significant figures appropriately in measurements and calculations.
- Discuss sources of measurement error and ways to reduce them.
- Choose rulers, Vernier calipers, micrometers, balances, clocks and measuring cylinders appropriately.
- Calculate and experimentally determine density.
Core notes
Measurement instruments
| Quantity | Suitable instrument | Key idea |
|---|---|---|
| Length of desk | metre rule | appropriate range; read at eye level |
| External/internal diameter | Vernier calipers | greater sensitivity than a metre rule |
| Wire/sheet thickness | micrometer screw gauge | very small length measurements |
| Mass | balance | zero/tare before use |
| Time | stopwatch/clock | repeat to reduce random timing error |
| Liquid volume | measuring cylinder | read meniscus at eye level |
Accuracy, sensitivity and range
Sensitivity concerns the smallest change an instrument can reliably detect. Range is the interval of values it can measure. Accuracy describes how close a measurement is to the accepted or true value. The most sensitive instrument is not always the most suitable if its range is inappropriate.
Density
density = mass ÷ volume. SI unit: kg m−3; g cm−3 is also common in laboratory work. Regular solids use geometrical volume; irregular solids can use displacement.
Video lesson
Paper 01-style MCQ
1. Which instrument is most suitable for measuring the diameter of a thin wire?KC • 1
2. A block has mass 240 g and volume 80 cm³. Its density isUK • 1
3. Which action best reduces random error when timing a repeated event?UK • 1
Paper 02-style structured questions
4. State THREE factors that should be considered when deciding whether an instrument is suitable for a measurement.UK • 3
Sensitivity/resolution (1); accuracy (1); range (1). Accept relevant reference to precision where clearly explained.
5. Describe how the density of an irregular stone can be determined using a balance and measuring cylinder.UK • 5
Measure mass using balance (1); record initial water volume (1); fully immerse stone and record final volume (1); stone volume = final − initial volume (1); density = mass ÷ stone volume with correct unit (1).
Experiment-type question
6. Plan an experiment to compare the densities of three different solid materials supplied as small irregular pieces.XS/PD • 8
State aim (1); measure mass of each sample (1); determine volume by water displacement (1); ensure samples are fully submerged and remove trapped air where possible (1); repeat measurements/use several pieces where practical (1); calculate density with units (1); compare calculated densities (1); include a source of error/precaution such as meniscus reading or splashing (1).