Friction Transfers Energy

Overview

Students investigate how different surfaces affect the force needed to pull the same object. They collect numerical data, calculate means, graph results, and use evidence to recommend a surface for a practical purpose such as sports shoes, bicycle brakes, or playground flooring.

Learning intentions

• WALT plan and carry out a fair test of friction.
• WALT describe friction as a force that transfers mechanical energy into thermal energy.
• WALT record, process, and graph investigation data.
• WALT use evidence to justify a recommendation for a chosen purpose.

Success criteria

• I can identify the independent, dependent, and controlled variables.
• I can measure pulling force consistently and record repeated results with units.
• I can construct and interpret a suitable graph.
• I can recommend a surface and explain my decision using data and energy concepts.

Curriculum links

• Demonstrate understanding of a physical system using energy concepts: describe change in the system using evidence, including energy transfer and conservation.
• Demonstrate understanding of a physical phenomenon through investigation: gather numerical data and use processed evidence such as tables, calculations, and graphs.
• Use the New Zealand Curriculum science capabilities of thinking, participating and contributing, managing self, and using language, symbols, and texts.
• Develop fair testing, accurate measurement, collaborative problem-solving, and evidence-based communication.

Lesson structure (50 minutes)

1. 0–5 min · Hook and prediction. Teacher opens the friction hook and learning-intentions slides with a visual comparison of a runner, bicycle brake, and playground surface, then asks, “Should the surface with the greatest friction always be chosen?” Students make a prediction and briefly justify it in pairs.

2. 5–12 min · Teach the key ideas. Teacher uses the friction, variables, and energy-transfer slides to explain friction as a contact force opposing motion, and as an energy transfer from mechanical energy to thermal energy; model how to read a spring scale at steady speed. Students identify the physical system, write the variables, and answer a quick check: “Where does the transferred energy go?”

Establish:

• Independent variable: surface.
• Dependent variable: pulling force.
• Controls: same object, load, spring scale, direction, distance, and approximately steady speed.
• Repeated trials improve reliability; a larger force generally indicates greater friction under the same conditions.

3. 12–16 min · Practical briefing and setup. Teacher demonstrates attaching the spring scale, pulling horizontally and steadily, reading the scale without jerking, and recording units in newtons. Teacher distributes the friction investigation worksheet and assigns groups of three with roles: equipment manager, puller, and data recorder. Students predict the ranking of three or four available surfaces and check their group’s method before beginning.

4. 16–29 min · Investigate. Teacher circulates, checks safe handling and fair testing, and prompts groups to repeat each surface at least three times. Students pull the same object across each surface, record the force for each trial, note observations, and calculate a mean force for each surface. If a reading fluctuates, students record the agreed method for choosing a consistent reading rather than selecting a convenient result.

5. 29–39 min · Process and graph data. Teacher pauses the class to model a graph on the graphing and data-analysis slides, including a descriptive title, labelled axes, units, and an appropriate scale. Students complete their results table and create a graph comparing surface with mean pulling force, by hand or using a spreadsheet if available. They identify the surface with the greatest and least average force and describe any unusual result.

6. 39–47 min · Apply and explain. Teacher displays the recommendation discussion slides and gives each group one purpose: sports shoes, bicycle brakes, or playground flooring. Students write a short recommendation on the worksheet using the structure: “For ___, I recommend ___ because…”. They must refer to at least two data points and explain that friction transfers mechanical energy into thermal energy. Groups share one recommendation; the class considers why maximum friction may not be ideal for every purpose.

7. 47–50 min · Exit check. Teacher asks students to complete the final section of the conclusion and exit-ticket section independently: “Describe one change to the system, identify the energy transfer, and give one improvement to this investigation.” Students hand in the worksheet or submit a clear photograph of their final response.

Resources

• the complete friction investigation slide deck
• the friction investigation worksheet
• Spring scales, one per group
• Identical objects to pull, such as wooden blocks
• Three or four labelled surface samples
• Masses or books to keep the load constant
• Metre rulers or tape measures
• Graph paper, rulers, pencils, and calculators
• Optional devices with spreadsheet software
• Safety glasses and a clear practical workspace

Assessment

• During teaching, ask students to identify the variables and explain where energy goes; correct confusion before the practical begins.
• Check group tables for repeated measurements, units, consistent technique, and calculated means. Question students about anomalous results and reliability.
• Assess the graph and recommendation for accurate processing, evidence-based reasoning, and correct use of friction and energy-transfer concepts. Use the exit response to identify next-step teaching.

Differentiation

• Provide the worksheet with a worked example, a variable bank, a graph template, and sentence starters: “The mean force for ___ was…”, “This shows…”, and “Energy was transferred from ___ to ___.”
• For dyslexia-friendly access, use a clear sans-serif font, generous spacing, short instructions, uncluttered tables, high-contrast labels, and allow students to hear instructions or use text-to-speech. Read key terms aloud and pair written directions with the teacher demonstration.
• Support EAL learners with labelled equipment, visual demonstrations, a bilingual glossary where available, and structured talk before writing. Give groups clearly defined roles and allow oral explanations before recording.
• Extension: students compare the spread of repeated results, calculate a range, discuss whether the mean is representative, and propose a further investigation such as changing the load or testing a wet surface. Advanced students should evaluate the trade-off between grip, wear, comfort, and energy loss for their chosen purpose.