Science 7–10 · Year 10

Ticker-tape analysis: velocity-time graph of a trolley rolling down a ramp

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, and this investigation measures acceleration without measuring a force or varying a mass, so only Year 10 inquiry codes are cited, as on the two speed entries before it)

Practical, model not builtLow risk

This site has no interactive model of its own. Where a step or a material names a Concept Studio model, simulation or tool, it has not been built; an external simulation a step names (for example PhET) is not part of this site.

The idea

A trolley rolling down a ramp gains speed at a steady rate, which appears as ticker-tape dots spreading out evenly and as a straight rising line on a velocity-time graph whose gradient is the acceleration.

What you need

ticker timer (50 Hz) with carbon disc and 12 V AC supply, 1
ticker tape, 2 m per run
dynamics trolley, 1
ramp 1.2 m with a clamp to set its height, 1
metre rule, ruler, scissors, glue stick, 1 set
graph paper

How to do it

Set the ramp at about 10 degrees. Fix the timer at the top and thread 1.5 m of tape through it and onto the trolley.
Switch on the timer and release the trolley from rest; switch off when it reaches the bottom. Repeat for a second tape.
Discard the first few crowded dots. Mark off the tape in ten-dot lengths (each 0.20 s at 50 Hz) and cut them out.
Glue the strips side by side in order on graph paper to make a bar chart of average velocity for each 0.20 s interval; measure each strip in centimetres and convert to m/s (length divided by 0.20 s).
Draw the line through the strip tops; find the acceleration from its gradient (change in velocity divided by time).
Raise the ramp to 20 degrees and repeat; compare accelerations.

What you should see

The dots start close together and spread out evenly along the tape. Consecutive ten-dot strips grow by a constant amount: for an acceleration of 1.0 m/s^2 each strip is 4.0 cm longer than the one before (a x (0.20 s)^2), and consecutive single dot gaps grow by 0.40 mm. The strip tops lie on a straight line. Without friction a 10 degree ramp would give g sin 10 = 1.70 m/s^2; friction on the wheels and the tape makes the measured value lower (the model below gives 1.41 m/s^2 for a rolling friction coefficient of 0.03). At 20 degrees the acceleration roughly doubles: 3.35 m/s^2 without friction and 3.08 m/s^2 in the model. The learner knows it worked when the strip-length differences are all about equal.

What changes

What you change: ramp angle (degrees)
What you measure: acceleration from the gradient of the velocity-time graph (m/s^2)
What you keep the same: same trolley
release from rest at the same point
tape threaded straight so it does not drag

Common misconceptions

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

Evenly spaced dots mean the trolley is accelerating.
A straight rising velocity-time line means constant speed.
The steeper ramp gives a higher final speed but the same acceleration.

Safety card

Low riskLearners carry it out

Hazards

trolley running off the bench
12 V AC timer terminals
scissors

Controls

a catcher or padded stop at the ramp foot
timer connected before switching on the supply

Note

Heat or electrical energy is involved. Complete the school's risk assessment for the activity before the lesson, using CSIS 1.7 (Risk assessment – a pre-requisite for risk control) from the department's Chemical Safety in Schools package (2021 Technical Update), which the NSW Department of Education Science safety and compliance page names for risk assessment advice.

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-02 SC5-WS-01 SC5-WS-05 SC5-WS-06
Australian Curriculum v9AC9S10I03AC9S10I04AC9S10I05

Sources

The pages the author read to write this activity.

All Concept Studio activities