Physics 11–12 · Year 11
Creating mechanical waves on a slinky: transverse, longitudinal and the role of the medium (syllabus practical)
Module 3: Waves and Thermodynamics (Wave Properties)
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The idea
A mechanical wave transfers energy through a medium whose particles oscillate about fixed positions, either across or along the direction of travel.
What you need
- Long metal slinky or long demonstration spring laid on a smooth floor and stretched a few metres (not so far that it stays deformed), and a plastic slinky for comparison
- Coloured wool tied to one coil as a marker, stopwatch, tape measure
- Phone video for slow-motion playback
How to do it
- Stretch the slinky along a smooth floor with one end held fixed; send a single transverse pulse and watch the marker: it moves across the slinky and returns.
- Send a longitudinal pulse by pushing the end forward and back; the marker moves along the slinky and returns as the compression passes.
- Measure the stretched length and time a pulse over several trips along it (slow-motion video makes the timing easier) to get its speed; repeat five times.
- Increase the tension by stretching further and time again; then compare the plastic slinky.
- Send a continuous wave and count the wavelength from the video; check v = f x lambda.
What you should see
Pulses travel at a constant speed for a given tension, and faster when the slinky is stretched more; the marker returns to its place after the pulse passes, showing that the medium does not travel with the energy. Pulses reflect inverted from the fixed end. The learner knows it worked when the product f x lambda agrees with the timed speed within about 10 per cent.
What changes
- What you change
- tension in the slinky
- What you measure
- pulse speed
- What you keep the same
- same slinky
- same pulse size
- same measured length
Common misconceptions
Each of these ideas is wrong, and the activity is a chance to test it.
- The coils travel along with the wave; each coil oscillates about a fixed position.
- A bigger amplitude makes the wave faster; speed depends on the medium and its tension, not on amplitude.
Safety card
Hazards
- slinky recoiling into a face when released
Controls
- release only when both ends are held
- clear floor space
Note
Record the activity in RiskAssess (https://www.riskassess.com.au/) and follow the Science ASSIST risk management information sheet (https://asta.edu.au/resource/ais-risk-management-and-risk-assessment/).
Curriculum references
The NSW syllabus outcomes and Australian Curriculum v9 codes this activity supports. They are references, not a verified or complete curriculum alignment.
- Physics Stage 6 Syllabus (2017), current: Year 11 until the end of 2026, Year 12 until Term 3 2027PH11-10PH11/12-3PH11/12-7
- Physics 11-12 Syllabus (2025), not yet taught: Year 11 from Term 1 2027, Year 12 from Term 4 2027, first HSC examination 2028PY-11-02PY-11WS-03
- Australian Curriculum v9No Australian Curriculum v9 code is listed.
Sources
The pages the author read to write this activity.
- www.nsw.gov.au/sites/default/files/noindex/2025-03/physics-stage-6-syllabus-2017.docx
- education.nsw.gov.au/content/dam/main-education/teaching-and-learning/curriculum/key-learning-areas/science/s-6/physics/Physics-module-3-guide.docx
- phet.colorado.edu/en/simulations/wave-on-a-string
- curriculum.nsw.edu.au/learning-areas/science/physics-11-12-2025/outcomes