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A1.1 · Form scientific questions, predictions, and testable hypotheses

Learn to form scientific questions, predictions, and testable hypotheses through clear examples and targeted practice.

Ontario Grade 12 Physics

Scientific Investigation Skills and Career Exploration

SPH4U A1.1: Form scientific questions, predictions, and testable hypotheses

Physics investigations begin with questions, not conclusions. A useful question identifies something that could be observed or measured. A prediction states what you expect to happen. A testable hypothesis connects a proposed change to an expected result in a way that evidence could support or challenge. These are different parts of planning an investigation. None is a substitute for actually collecting evidence. This lesson focuses on forming these questions, predictions, and hypotheses clearly.

What you will learn

Distinguish a scientific question, a prediction, and a testable hypothesis.
Identify the system, reference frame, and variables relevant to a proposed physics investigation.
Use a physics model to make a prediction without claiming that it is measured evidence.
Judge whether a hypothesis can be tested with observable evidence.

1. From a physics idea to a scientific question

A scientific question asks about a relationship or outcome that can be investigated using observations or measurements. A broad topic such as motion is not yet a question. A question such as “How does the ramp’s angle affect the time a cart takes to travel a fixed distance?” is more useful. It identifies a change to investigate and an outcome to measure.

Before planning a physics investigation, name the system: the object or group of objects being studied. For the cart question, the system is the cart. State the reference frame, the viewpoint used to describe position and motion. For example, the cart’s motion can be described relative to the ramp. Choose and state a positive direction, such as down the ramp. This makes descriptions like “moves in the positive direction” unambiguous.

A scalar has magnitude only, such as time or distance. A vector has magnitude and direction, such as displacement or velocity. If an investigation asks about a vector, specify how its direction will be recorded. Keeping these distinctions clear makes the question measurable and the later evidence easier to interpret.

A focused question names the changing condition and the observable outcome.
State the system, reference frame, and positive direction when they matter to the investigation.
Decide what evidence could answer the question before proposing a procedure.

2. Variables and a testable hypothesis

A variable is a feature that can have different values. The independent variable is the factor deliberately changed. The dependent variable is the outcome measured or observed. Controlled variables are conditions kept the same so that the effect of the independent variable is easier to interpret. For the cart question, ramp angle could be independent, travel time could be dependent, and the cart and measured travel distance could be controlled.

A testable hypothesis is a proposed relationship between variables that could be checked using evidence. A clear form is: “If [independent variable changes], then [dependent variable is expected to change in a stated way], because [physics reasoning].” The “because” should connect to a suitable course-level model or principle. It should not claim that the proposed result has already been observed.

A prediction states an expected result for a particular condition. It may be qualitative, such as expecting a shorter travel time, or quantitative, such as predicting a value when the relationship and required information are available. A hypothesis is broader: it proposes a relationship that can be tested across conditions. A prediction can follow from that hypothesis.

A hypothesis is testable when the variables can be observed or measured and the expected result could, in principle, be compared with evidence. A claim that cannot be checked by any observation or measurement is not a useful testable hypothesis for a physics investigation. Testability does not mean the hypothesis is already correct.

\text{If }

x changes, then y is expected to change because \ldots

Independent variable: deliberately changed factor.
Dependent variable: measured or observed outcome.
Controlled variables: conditions kept the same.
A testable hypothesis makes an evidence-checkable claim; it is not a confirmed result.

3. Use a model to make a prediction

A physics model is a simplified description used to connect conditions with expected outcomes. Before using one, state the conditions under which it is being applied. For example, a model may describe motion along a straight ramp while the same cart and travel distance are used. These limits keep the prediction tied to the proposed situation.

For an object moving at a steady speed, the relationship between distance, speed, and time is

v = d/t

. Here,

v

is speed in metres per second,

d

is distance in metres, and

t

is time in seconds. This relationship can help form a prediction when speed or distance is specified. It does not provide measured results for a proposed investigation.

A useful planning sketch can show the system and the measurement. For the ramp example, draw a cart on a ramp, mark the fixed start and finish points, and label the ramp angle as the condition to vary. If using a motion graph, label the horizontal axis with time in seconds and the vertical axis with position in metres. A labelled sketch helps make clear what is changing and what is being recorded.

Predictions should be checked for sensible units and meaning. A predicted time should have units of seconds and should be positive. If the prediction concerns direction, it should match the stated positive direction. A calculation can support a prediction, but it is not evidence that the event occurred.

v = \frac{d}{t}

State the model and relevant conditions before using it.
Use units and direction consistently in a prediction.
A model-based prediction is not a measurement.

4. Evidence, procedure, and careful wording

A proposed procedure describes how evidence could be collected. It is a plan, not a report of what happened. Measured evidence consists of actual recorded observations or measurements. Do not write a predicted value as though it were measured. If a simulation is used, identify its output as simulated evidence rather than a physical measurement.

A strong investigation question is narrow enough that a procedure could address it. It also avoids suggesting that a particular result is already certain. Words such as “prove” often make a question less careful. Evidence may support a hypothesis, disagree with it, or be too uncertain to decide. A hypothesis remains a proposal until evidence is considered.

When planning, ask whether the proposed measurement directly represents the dependent variable, whether the independent variable can be changed, and whether important conditions can be kept consistent. Also consider whether the measurement has suitable units and a clear method of recording direction when relevant. These checks improve the question and hypothesis before evidence is collected.

Do not add a causal explanation that the proposed investigation cannot examine. If several conditions change together, it may be unclear which one relates to the outcome. Narrowing the question and naming controlled variables makes the intended comparison clearer.

A procedure is proposed; measured evidence is collected.
Describe simulated outputs as simulated, not as physical measurements.
Use cautious wording: evidence can support or challenge a hypothesis.

Worked example

Improve a broad question

A student wants to investigate “ramps and carts.” Turn this topic into a focused scientific question and identify its system and frame.

Name the system and frame
Choose the cart as the system. Describe its motion relative to the ramp, and take down the ramp as the positive direction.
Choose a change and an outcome
A ramp’s angle can be changed, while the time for the cart to travel between fixed points can be measured. The cart and travel distance can be kept the same.
Write the focused question
Ask how changing the ramp angle affects the cart’s travel time over the same distance. This question identifies a condition and an observable outcome without assuming the answer.

Answer: How does the ramp angle affect the time a cart takes to travel a fixed distance? The system is the cart, and the reference frame is the ramp.

Check: The question can guide a proposed measurement of time while the angle changes. It does not claim that any measurements have already been made.

Worked example

Build a testable hypothesis

For the cart and ramp question, form a hypothesis that gives an expected relationship and a reason. Do not present it as a result.

State the variables
Use ramp angle as the independent variable and travel time as the dependent variable. Keep the cart and travel distance the same.
Connect to a model
For a fixed distance, the speed relationship $v = d/t$ shows that a greater average speed corresponds to less time. This relationship alone does not establish what speed the cart will have at a particular angle, so phrase the claim as an expectation to test.
Write the hypothesis
State the expected direction of change and give a reason linked to the proposed motion. Treat the statement as a prediction about a possible investigation, not as measured evidence.

Answer: If the ramp angle is increased while the cart and travel distance remain the same, then the cart is expected to take less time, because a steeper ramp is expected to produce faster motion along the ramp. This is a testable hypothesis, not a confirmed finding.

Check: The expected outcome is measurable in seconds, and the changed condition is identified. The proposed reason is a model-based expectation that would need evidence.

Worked example

Make a prediction for a stated model

A proposed model describes an object travelling at a steady speed of

2.0\,\mathrm{m/s}

over a distance of

6.0\,\mathrm{m}

. Predict its travel time. Treat the values as supplied model conditions, not collected data.

Define the situation
The system is the object. Use the path as the reference frame and take the direction of travel as positive. The known values are speed and distance; the unknown is time.
Choose the relationship
For steady speed, use distance divided by speed to find time. The units should reduce to seconds.
$t = \frac{d}{v}$
Substitute and calculate
Substitute the supplied values with units. The result has two significant figures, matching the given values.
$t = \frac{6.0\,\mathrm{m}}{2.0\,\mathrm{m/s}} = 3.0\,\mathrm{s}$

Answer: The model-based prediction is

3.0\,\mathrm{s}

Check: Metres divided by metres per second gives seconds. The positive time is reasonable for a positive distance and speed. It is a prediction from supplied model conditions, not a measured travel time.

Common mistakes and how to avoid them

Writing a topic such as “electricity” as though it were a scientific question.

Correction: Ask about a measurable outcome and name the condition being changed.

Calling a prediction a measured result.

Correction: Label expected outcomes as predictions. Report measurements only after they have actually been collected.

Changing several factors at once without identifying them.

Correction: Name the independent, dependent, and controlled variables so the intended comparison is clear.

Saying a hypothesis is proven because it matches one expected outcome.

Correction: Treat it as a proposed relationship. Evidence can support or challenge it.

Leaving direction unclear when studying a vector quantity.

Correction: State a reference frame and positive direction, then use them consistently.

Lesson summary

A scientific question is focused on an observable or measurable outcome.
A prediction states an expected result; a testable hypothesis proposes an evidence-checkable relationship.
Identify the system, reference frame, direction when relevant, and investigation variables.
Use a course-level model carefully, including units and conditions.
Keep proposed procedures, predictions, measured evidence, and simulated outputs distinct.

Check your understanding

Question 1

Which is the clearest testable question?

Why are carts interesting?
How does changing a cart’s load affect the time to travel a fixed distance?
Will the cart definitely move faster?
What is the best ramp?

Show answer and explanation

How does changing a cart’s load affect the time to travel a fixed distance?

It identifies a factor that can be changed and an outcome that can be measured. The other choices are vague or assume a conclusion.

Question 2

A student writes, “If the ramp angle increases, travel time will decrease.” What kind of statement is this when it is proposed before evidence is collected?

A measured result
A testable hypothesis
A controlled variable
A reference frame

Show answer and explanation

A testable hypothesis

It proposes a relationship that can be checked by measuring travel time at different angles. It is not measured evidence.

Question 3

A model gives a steady speed of

3.0\,\mathrm{m/s}

over

9.0\,\mathrm{m}

. What travel time does it predict?

$0.33\,\mathrm{s}$
$3.0\,\mathrm{s}$
$12\,\mathrm{s}$
$27\,\mathrm{s}$

Show answer and explanation

3.0\,\mathrm{s}

Using

t = d/v

, the time is

9.0\,\mathrm{m}/(3.0\,\mathrm{m/s}) = 3.0\,\mathrm{s}

. The units reduce to seconds.

Key terms

System: The object or group of objects being studied.
Reference frame: The viewpoint relative to which position and motion are described.
Variable: A feature that can take different values.
Independent variable: The factor deliberately changed in an investigation.
Dependent variable: The outcome observed or measured.
Controlled variable: A condition kept the same to make a comparison clearer.
Prediction: A statement of an expected outcome under stated conditions.
Testable hypothesis: A proposed relationship that can be checked using observations or measurements.

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About this lesson and its review

Published by DoAssignment. This AI-assisted lesson follows Ontario Grade 12 Physics (SPH4U), expectation A1.1. It is a study resource, not an official curriculum publication.

Before publication, the draft is checked for structure, mathematical or chemical notation, calculations, course boundaries, and readability, and then requires administrator approval. Errors can still occur, so corrections are welcomed.

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