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Science 7–10 · Year 10

Average speed of a battery toy car over measured distances

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

Speed is the distance travelled divided by the time taken, and a car moving at constant speed covers equal distances in equal times.

What you need

  • battery-powered toy car that runs at a steady speed, 1
  • 5 m tape measure, 1
  • stopwatches, 3
  • 100 g slotted mass to sit on the car, taped down, 1
  • masking tape marks at 0, 1.0, 2.0, 3.0 and 4.0 m
  • smooth floor 5 m long

How to do it

  1. Start the car 0.5 m before the zero mark so it is at full speed when it crosses it.
  2. Three timers start their watches as the front of the car crosses zero and stop at 1.0, 2.0 and 3.0 m respectively. Record all three times. Repeat for five runs.
  3. Average the times for each distance and plot distance against average time.
  4. Draw the line of best fit and read its gradient: the car's speed in m/s.
  5. Calculate speed separately for each distance (distance / time) and compare with the gradient.
  6. Add a 100 g load to the car and repeat two runs; compare the speed.

What you should see

For example, a car covering 2.0 m in 4.0 s has a speed of 0.50 m/s and reaches the 3.0 m mark at about 6.0 s. The distance-time points lie on a straight line through the origin, and the speeds calculated for each distance agree with the gradient within the scatter caused by reaction time. The loaded car may run slower. The learner knows it worked when the five-run times at each mark agree closely and the points lie on a straight line.

What changes

What you change
distance travelled (m)
What you measure
time taken (s)
What you keep the same
  • same car and batteries
  • flying start before the zero mark
  • same floor

Common misconceptions

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

  • Average speed is the speed halfway through the run.
  • A longer distance means a faster speed.
  • The stopwatch measures speed.

Safety card

Low riskLearners carry it out

Hazards

  • tripping on the car or tape

Controls

  • timers stand to the side of the track

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.

Sources

The pages the author read to write this activity.

  1. curriculum.nsw.edu.au/learning-areas/science/science-7-10-2023/outcomes
  2. curriculum.nsw.edu.au/learning-areas/science/science-7-10-2023/content/stage-5/faafd3c3df
  3. spark.iop.org/collections/time-distance-and-speed
  4. spark.iop.org/ticker-timers-investigating-speed

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