Physics 11–12 · Year 11

Average and instantaneous velocity from a ticker-timer tape (syllabus practical)

Module 1: Kinematics (Motion in a Straight Line)

Practical, model not builtLow risk

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The idea

A dot pattern made at a known rate turns a moving trolley into a position-time record from which average and instantaneous velocity are read as gradients.

What you need

Ticker timer (recording timer) marking 50 dots per second on a 12 V AC laboratory supply, with carbon disc
Ticker tape, about 1.5 m per run
Dynamics trolley (about 0.5 kg) and a 1.2 m runway or bench
Motorised toy car for a constant-velocity run (as in the NSW Department of Education Module 1 guide)
Metre rule graduated in millimetres, sticky tape, graph paper or spreadsheet

How to do it

Thread the tape through the timer, attach it to the trolley and check that the timer marks 50 dots per second (each gap is 0.020 s).
Run 1: switch on the timer and push the motorised car so it moves at constant speed; run 2: release the trolley from rest down a runway raised at one end.
Cut each tape into strips of five gaps (0.10 s) and measure each strip length to the nearest millimetre.
Tabulate time (0.10 s steps) against cumulative distance, and plot position against time.
Average velocity over the whole tape is total displacement divided by total time; instantaneous velocity at a dot is the gradient of the tangent there, estimated as strip length divided by 0.10 s.
Plot velocity against time; the gradient is the acceleration. Repeat each run three times and compare gradients.

What you should see

Constant-speed tape: equal dot spacing, a straight position-time line. Accelerating tape: spacing grows steadily; five-gap strips of 2.0, 3.0 and 4.0 cm (each 0.10 s) give velocities of 0.20, 0.30 and 0.40 m/s at their mid-times and an acceleration of 1.0 m/s^2 (a velocity change of 0.20 m/s over 0.20 s). The learner knows it worked when the velocity-time points lie on a straight line within about 5 per cent scatter.

What changes

What you change: time since release
What you measure: position and velocity of the trolley
What you keep the same: timer frequency 50 Hz
runway angle
same trolley and tape

Common misconceptions

Each of these ideas is wrong, and the activity is a chance to test it.

A longer strip means more time passed; in fact every strip covers the same 0.10 s and a longer strip means a faster trolley.
Average velocity is the average of the first and last readings; that only holds for constant acceleration.

Safety card

Low riskLearners carry it out

Hazards

12 V AC timer terminals
trolley running off the bench

Controls

use the low-voltage laboratory supply only
catch box at the end of the runway

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 2027PH11-8 PH11/12-3 PH11/12-4 PH11/12-5
Physics 11-12 Syllabus (2025), not yet taught: Year 11 from Term 1 2027, Year 12 from Term 4 2027, first HSC examination 2028PY-11-01 PY-11WS-04
Australian Curriculum v9No Australian Curriculum v9 code is listed.

Sources

The pages the author read to write this activity.

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