Course 239 · Life course 61

Explain Motion and Forces

A fictional cart-motion report with position and velocity graphs, net-force reasoning, a mass/acceleration comparison and a checked prediction. Six introductory lessons use supplied practice cases.

Before you start

Use paper or a free text document; every core input is supplied in the lessons.

Read and Build Linear Functions See everything you’ll need

Free download · Original practice data · No external account required. Download the starter pack

What you’ll leave with

A fictional cart-motion report with position and velocity graphs, net-force reasoning, a mass/acceleration comparison and a checked prediction.

Start course Start without an account. Sign in to save lesson progress across devices.

Your project

Start with the practice files. Build your project one lesson at a time.

Practice files are free without an account. Sign in to save your project record in My Proof: a description, checklist, and optional work link. Keep the original files in your own app or notebook; saving a project record does not upload them.

Get your materialsDownload practice filesSupplied practice cases, a blank working record, complete lesson instructions, and annotated worked examples.
Make your projectView the project checklist Work in your own notebook, document, or software. Use the supplied practice examples when you prefer.
Keep a private recordSave a project record Sign in to save a description and checklist, then return to update them.

Course handbook

Know the route before you begin.

Here’s what you’ll need and what you’ll make. You can return to this guide during any lesson.

Who this is for

Learners aged 14+ building subject foundations and practical independence. Adults can use the same supplied cases.

Prepare before lesson one

Use paper or a free text document; every core input is supplied in the lessons.
A basic calculator is optional; show the method, units and checks.
Suggested earlier course: Read and Build Linear Functions

Your final project

Finish with proof you can use.

A fictional cart-motion report with position and velocity graphs, net-force reasoning, a mass/acceleration comparison and a checked prediction.

Save a project record in My Proof

See project checklist and review criteria

Keep your working files in your own notebook or software. Save a private description, checklist, and work link in My Proof.

What to include

Define a reference frame and calculate distance versus displacement.
Plot the supplied position-time graph and compute both averages.
Calculate acceleration from velocity change.
Draw a one-object force diagram and sum components.
Compare masses under fixed net force.
Test the final prediction against supplied data and include changed cases.

Review and revise

Use these criteria to check your work and choose what to improve.

Method: applies the course-specific rules to the supplied cases with visible intermediate work.
Accuracy: results agree with the stated facts, units, boundaries and independent checks.
Reasoning: explains why the result follows and identifies a limitation or unresolved question.
Transfer: completes changed cases and revises the final project when a relevant assumption changes.

Three ideas to help you along the way

Three useful ideas

The rules behind the steps.

Read the specific conditions

Position needs a reference point, a direction and units. Displacement is final minus initial position; distance is the total path length. A round trip can have positive distance and zero displacement. Keep the coordinate convention fixed while calculating.

Connect the mechanism

Average acceleration equals change in velocity divided by elapsed time. Its units are meters per second per second. A negative acceleration is not automatically slowing: compare its direction with velocity. For a positive-moving object, negative acceleration reduces positive velocity over the stated interval.

Explain evidence and limits

A prediction depends on explicit conditions. Under constant net force and mass, acceleration is constant; use v=v0+at to predict the supplied interval. Compare model and observed values before claiming agreement. A mismatch can point to an incomplete model or measurement, not automatically one cause.

What do these words mean?

Key words

Key terms worth knowing.

Reference frame: A stated origin, axes and viewpoint for describing motion.
Displacement: Signed change from initial to final position.
Average speed: Total path distance divided by elapsed time.
Velocity: Rate of position change with direction.
Acceleration: Rate of velocity change.
Net force: Directional sum of forces acting on the selected object.

Your route

6 lessons.
One useful project.

Work in order the first time. Each lesson makes something the next lesson can use.

Use the tools

Tools to help you practice.

See all tools

ZIP · practice files

Explain Motion and Forces practice files

Supplied practice cases, a blank working record, complete lesson instructions, and annotated worked examples.

Text worksheet

Your course project worksheet

A downloadable text worksheet with each lesson’s working output, space for your answers, and the shared final-project checklist. Save your own copy.

Source transparency

Sources and further study.

Explore the references behind the lessons and take your learning further. Source notes explain access and reuse.

OpenStax: position, distance and displacement

Source & access notes · checked 2026-10-01

Web open/search showed the official page, its topic heading and relevant concept description. This is a content/source check, not a provider endorsement.