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A1.5 · Conduct inquiries safely while controlling relevant variables

Learn to conduct inquiries safely while controlling relevant variables through clear examples and targeted practice.

Ontario Grade 11 Physics

Scientific Investigation Skills and Career Exploration

Planning a fair, useful, and safe physics investigation

A physics inquiry is a planned way to investigate a question. A useful inquiry needs evidence that relates to the question. It also needs a safe procedure and a plan for relevant variables. A variable is a factor that can change. In this lesson, you will practise identifying variables, planning fair comparisons, and deciding how to work safely. The examples are proposed plans, not reports of completed experiments.

What you will learn

Explain how safety decisions shape an inquiry.
Identify the independent, dependent, and controlled variables in an investigation.
Plan a procedure that changes one relevant factor while keeping other relevant factors consistent.
Distinguish evidence collected in a real investigation from predictions or simulation results.

1. Start with the question and the safety plan

A scientific inquiry begins with a question that can be investigated. A focused question names a factor to change and an outcome to observe. For example, a class might ask how changing the ramp height affects the distance a cart travels after leaving the ramp. This is a proposed question; it does not claim that any measurements have been made.

Before collecting evidence, identify possible hazards. A hazard is something that could cause harm, such as a moving object, a trip hazard, or equipment that could fall. Risk is the chance that harm could occur. A safety plan describes steps that reduce risk. Follow the teacher’s instructions and the rules for the room and equipment. If a task seems unsafe or the setup changes, stop and ask the teacher before continuing.

Make the area orderly. Keep bags and loose items away from the work space. Check that equipment is stable and in suitable condition. Keep people clear of the path of moving objects. Use required protective equipment and handle equipment only as instructed. Do not begin until the teacher has approved the procedure when approval is required.

Safety is part of the procedure, not an extra step after the investigation. If a method creates an avoidable hazard, change the method or do not carry it out. A result is not worth risking someone’s safety.

Write a focused, investigable question.
Identify hazards before starting and reduce risks using the approved procedure.
Stop and seek guidance if the setup is unsafe or unclear.

2. Identify the variables

A variable is a factor that can take different values or conditions. The independent variable is the factor deliberately changed to investigate a question. The dependent variable is the outcome observed or measured. Controlled variables are relevant factors kept as consistent as possible so the comparison is meaningful.

In the ramp question, ramp height is the independent variable. The distance the cart travels after leaving the ramp is the dependent variable. The cart, ramp surface, release method, and measurement method could be controlled variables. They matter because changing them at the same time could also affect the distance.

A fair comparison changes the independent variable while keeping relevant controlled variables consistent. This does not mean that every detail in the room must be identical. Focus on factors that could affect the outcome being studied. If a factor cannot be kept exactly the same, note it and consider how it may affect the evidence.

Decide how the dependent variable will be observed before collecting evidence. For example, describe where distance begins and ends, and what tool or method will be used to determine it. A clear measurement method makes it easier for different trials to be compared. Record observations with units when the quantity has units, and write down relevant conditions rather than relying on memory.

Independent variable: deliberately changed factor.
Dependent variable: observed or measured outcome.
Controlled variables: relevant factors kept consistent.
Define how the outcome will be observed before starting.

3. Plan, carry out, and review the inquiry

Before starting, write a procedure that another student could follow. Include the equipment, the sequence of actions, how the independent variable will be changed, how the dependent variable will be recorded, and which factors will be kept consistent. Include safety steps where they apply. A useful procedure is specific enough to reduce guesswork but does not promise a result.

During an inquiry, record what was actually observed or measured. These records are evidence. Keep measured evidence separate from a prediction, an explanation, or a result produced by a simulation. A simulation can help explore a model, but its output is not a measurement made in a physical investigation. Label the source of information clearly.

When suitable and safe, repeat observations under the same conditions. Repeated trials can show whether results are consistent or whether an unusual result needs attention. Do not discard a result just because it differs from others. Check the procedure and recording, and follow the teacher’s direction about how to handle it.

After collecting evidence, check whether the procedure answered the question. Ask whether the independent variable changed as planned, whether the dependent variable was recorded consistently, and whether controlled variables stayed consistent. Describe limitations honestly. A limitation is a feature of the method that may affect how confidently the evidence answers the question. Do not claim more than the evidence supports.

Write the procedure and safety steps before collecting evidence.
Record actual observations separately from predictions and simulation outputs.
Review whether variables were handled as planned and describe limitations honestly.

4. Use a planning checklist

A checklist helps catch problems before an inquiry begins. First, confirm that the question can be investigated safely with the available equipment and teacher guidance. Next, name the independent and dependent variables. Then list relevant controlled variables and explain how the procedure will keep them consistent.

Finally, define how observations will be recorded. Include units where they apply, keep records clear, and note any changes or difficulties. This planning does not guarantee a particular outcome. It improves the chance that the evidence will be relevant, interpretable, and collected safely.

Question: What factor will be changed, and what outcome will be observed?
Safety: What could cause harm, and what approved steps reduce the risk?
Variables: What changes, what is observed, and what stays consistent?
Evidence: What will be recorded, and how will actual observations be distinguished from other information?

Variable roles in an inquiry

Variable type	Meaning	Ramp inquiry example
Independent	Factor deliberately changed	Ramp height
Dependent	Outcome observed or measured	Cart travel distance
Controlled	Relevant factor kept consistent	Cart or release method

Worked example

Planning a ramp inquiry

A student proposes asking how ramp height affects how far a cart travels after leaving the ramp. Identify the variables and suggest a fair, safe plan. This is a planning example, not a completed investigation.

Name the variables
The question identifies ramp height as the factor to change, so it is the independent variable. The cart’s travel distance after leaving the ramp is the dependent variable because it is the outcome to observe. Keep the same cart, ramp surface, release method, and distance-measuring method where possible.
Make the plan fair
Change only the ramp height between conditions. Use the same release point and release method each time. State clearly where the distance begins and ends. Record the height condition and the observed distance for each trial, with units for measured quantities.
Check safety
Before the inquiry, ask the teacher to check the setup. Keep the cart’s path clear, secure the ramp as instructed, and keep people away from the moving cart. Do not proceed if the ramp is unstable or the path cannot be kept clear.

Answer: Ramp height is the independent variable; travel distance is the dependent variable. The cart, surface, release method, and measurement method are relevant controlled variables. The plan must also include a clear path and a stable, approved setup.

Check: The plan changes the factor named in the question, keeps other relevant factors consistent, and includes safety checks. No result is claimed because no measurements have been collected.

Worked example

Improving a sound-level inquiry

A proposed question asks whether distance from a sound source affects the sound level recorded by a meter. The first draft changes the distance and also changes the sound source. Explain why this is a problem and revise the plan.

Find the confounding change
The independent variable is distance from the source. The dependent variable is the sound level recorded by the meter. Changing the sound source as well means the observed difference could be related to either change, so the comparison would not clearly answer the question.
Control relevant factors
Use the same source and the same meter for each planned distance. Keep the source setting and the meter’s position and orientation consistent, and use the same recording method. These are proposed controls, not claims about measured results.
Plan safely
Use a sound level and duration approved by the teacher. Keep the work area clear and avoid placing equipment where someone could trip over it. If the source or setup could create an unsafe sound level, do not proceed; ask the teacher to revise the plan.

Answer: Changing both distance and source makes it unclear which factor is linked to any difference. Keep the source and measurement setup consistent while changing distance, and follow the teacher’s safety instructions.

Check: The revised plan changes one intended independent variable and controls relevant alternatives. It does not assume that any particular sound-level result will occur.

Worked example

Keeping evidence separate from a simulation

A group uses a simulation to explore how changing a selected setting affects a displayed motion outcome. They plan to report the simulation output as measurements from a physical investigation. What should they change?

Identify the source of information
The displayed outcome comes from a simulation, not from a physical object measured with equipment. The group should label it as simulation output and should not describe it as measured evidence from a physical investigation.
Control the comparison
For a clear comparison within the simulation, change the selected setting while keeping other relevant settings the same. Record the setting and the displayed outcome for each planned run. State that these are simulated results.
Describe the limits
Explain that the output depends on the simulation and its settings. Do not claim that the simulation proves what will happen in a physical setup. If a physical inquiry is also proposed, plan and carry it out separately, safely, and with teacher guidance.

Answer: Report the output as simulation results, not physical measurements. Keep other relevant simulation settings consistent when comparing runs, and describe what the simulation can and cannot support.

Check: The revised report identifies the evidence source accurately and does not present a proposed physical procedure as completed work.

Common mistakes and how to avoid them

Changing several relevant factors at once and treating the outcome as if it answers a single-factor question.

Correction: Change the independent variable while keeping other relevant factors consistent. If that is not possible, state the limitation.

Calling a prediction or simulation output a measurement from a physical investigation.

Correction: Label predictions, simulation outputs, and observations from physical investigations clearly as different sources.

Starting before considering hazards or continuing when the setup seems unsafe.

Correction: Review the approved safety steps first. Stop and ask the teacher if the procedure or setup is unsafe or unclear.

Writing a procedure that does not say how the outcome will be observed.

Correction: Define the measurement or observation method, including what is being recorded and units where they apply.

Lesson summary

Plan safety before beginning an inquiry, and follow teacher directions.
Identify the independent, dependent, and relevant controlled variables.
Change the intended factor and keep relevant alternatives consistent for a fair comparison.
Record actual observations clearly and distinguish them from predictions and simulation outputs.
Review whether the evidence answers the question, and describe limitations honestly.

Check your understanding

Question 1

A student investigates how the surface of a track affects a toy car’s travel distance. Which factor is the independent variable?

The track surface
The travel distance
The method used to record distance
correctIndex

Show answer and explanation

The track surface

The surface is deliberately changed, so it is the independent variable. Travel distance is the outcome being observed.

Question 2

Why should relevant controlled variables be kept consistent?

So any observed difference can be related more clearly to the factor being changed
So the inquiry is guaranteed to produce the expected result
So no observations need to be recorded
correctIndex

Show answer and explanation

So any observed difference can be related more clearly to the factor being changed

Keeping relevant factors consistent makes the comparison more meaningful. It does not guarantee a particular result.

Question 3

A screen in a simulation displays an outcome. How should the group describe that information?

As simulation output, separate from measurements in a physical investigation
As physical measurements, even if no physical equipment was used
As proof that the same outcome will occur in every real setup
correctIndex

Show answer and explanation

As simulation output, separate from measurements in a physical investigation

The result came from a simulation, so it should be labelled as simulation output. It is not a physical measurement.

Key terms

Inquiry: A planned investigation used to answer a question with evidence.
Variable: A factor that can change or have different conditions.
Independent variable: The factor deliberately changed in an inquiry.
Dependent variable: The outcome observed or measured.
Controlled variable: A relevant factor kept consistent during a comparison.
Hazard: Something that could cause harm.
Evidence: Recorded observations or measurements used to consider an inquiry question.
Limitation: A feature of a method that may affect how confidently its evidence answers the question.

Continue through SPH3U

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About this lesson and its review

Published by DoAssignment. This reviewed lesson follows Ontario Grade 11 Physics (SPH3U), expectation A1.5. It is a study resource, not an official curriculum publication.

Before publication, content is checked for structure, mathematical or chemical notation, calculations, course boundaries, and readability. Errors can still occur, so corrections are welcomed.

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