Science 7–10 · Year 10
Distance-time graphs: walking in front of a motion sensor (or along floor marks)
Physical sciences — Waves and motion: motion and Newton's laws (NSW Stage 5 focus area; ACARA's Year 10 physical sciences description, AC9S10U05, is about Newton's laws and the force, mass and acceleration relationship, which this investigation does not involve, so only Year 10 inquiry codes are cited)
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The idea
The gradient of a distance-time graph is speed, so walking steadily gives a straight line, standing still gives a flat line and walking back gives a falling line.
What you need
- ultrasonic motion sensor with data logger or laptop software, 1 (or a 10 m tape, floor marks every 1 m and a stopwatch)
- clear corridor or lab floor 8 m long
- masking tape, 1 roll
How to do it
- Set up the sensor at one end facing along the corridor and check its maximum range in the manual. One learner stands 1 m away, starts logging and walks slowly away at a steady pace for 3 s, stands still for 3 s, then walks back faster for 2 s, staying within the sensor's range throughout.
- Look at the live distance-time graph and label which part of the walk produced each section.
- Read the gradient of the first section (distance change divided by time) to find the walking speed; repeat for the return section.
- Without the sensor: mark the floor every 1.0 m, and time a learner passing each mark while walking steadily; plot distance against time by hand and find the gradient.
- Sketch a target graph that stays within the sensor's range (for example: 1 m/s for 3 s, stop 2 s, return at 0.5 m/s for 4 s) and have a learner try to walk it while watching the live trace.
What you should see
Steady walking away gives a straight rising line whose gradient is the walking speed; standing still gives a flat line; walking back gives a falling line, steeper when the return is faster. The hand-timed floor-mark method gives a gradient close to the sensor's for the same steady walk. The learner knows it worked when they can name the motion from the graph shape alone and reproduce a target graph by walking.
What changes
- What you change
- walking speed and direction
- What you measure
- distance from the sensor against time
- What you keep the same
- straight-line path
- sensor fixed
- walker facing the same way
Common misconceptions
Each of these ideas is wrong, and the activity is a chance to test it.
- A flat line on a distance-time graph means constant speed.
- A steeper line means the walker is further away.
- The graph is a picture of the path walked.
Safety card
Hazards
- walking backwards into furniture
- tripping on leads
Controls
- clear the path
- walk forwards on the return, turning first
Note
No hazardous chemicals or naked flames are used. Complete the school's risk assessment for the activity before the lesson; the NSW Department of Education Science safety and compliance page points to CSIS 1.7 (Risk assessment – a pre-requisite for risk control) for how to carry it out.
Curriculum references
The NSW syllabus outcomes and Australian Curriculum v9 codes this activity supports. They are references, not a verified or complete curriculum alignment.
- Science 7–10 Syllabus (2023)SC5-WAM-02SC5-WS-01SC5-WS-05
- Australian Curriculum v9AC9S10I03AC9S10I04
Sources
The pages the author read to write this activity.