Forces Change Motion

Overview

Students investigate force as a push or pull and explain how forces can change an object’s motion or shape. They use everyday objects to identify contact and non-contact forces, represent forces with arrows, and distinguish balanced from unbalanced forces.

Learning intentions

Students will:

• describe force as a push or pull measured in newtons.
• identify contact and non-contact forces in familiar situations.
• explain how forces can change motion, direction or shape.
• represent forces using labelled arrows and compare balanced and unbalanced forces.
• collect observations and use evidence to communicate an explanation.

Success criteria

• I can give examples of pushes, pulls, contact forces and non-contact forces.
• I can explain that a force is measured in newtons using the symbol N.
• I can draw arrows showing the direction and relative size of forces.
• I can decide whether forces are balanced or unbalanced and justify my answer.

Curriculum links

• Science understanding: forces can affect the motion and shape of objects.
• Science inquiry: students make predictions, observe patterns, record results and use evidence to explain findings.
• Science as a human endeavour: force concepts help explain familiar technologies, sports and transport.
• Broadly supports Queensland Year 7 science expectations and prepares students for later force-and-motion learning, including the force and motion connection in the QCAA senior Physics curriculum, without requiring senior Physics content.

Lesson structure (60 minutes)

1. 0–5 minutes – Hook and prior knowledge Open with the force hook and learning intentions. Ask students to silently identify every push or pull they can see in a short classroom scenario or image. Collect several examples and clarify that a force is an interaction involving a push or pull.

2. 5–15 minutes – Explicit teaching: force effects Use the force effects and examples slides to explain that forces may start, stop, speed up, slow down, change direction or change shape. Introduce the unit newton (N), explaining that a force meter or spring balance measures force in newtons. Demonstrate a light push and a stronger push on a book, asking: “What changed, and what evidence supports your answer?”

3. 15–22 minutes – Contact, non-contact and diagrams Model examples on the board: friction, air resistance and applied force are contact forces; gravity and magnetism are non-contact forces. Demonstrate a force diagram using a box: arrows point in the direction of the force, are labelled, and may be longer when the force is greater. Use the Forces Free-body Diagram Arrows for the demonstration and explain that balanced forces are equal and opposite, while unbalanced forces produce a change in motion.

4. 22–42 minutes – Practical investigation in groups Place students in groups of four with roles: equipment manager, pusher/puller, observer and recorder. Distribute the forces investigation worksheet and provide a book, toy car, ruler, rubber band, magnet and small paper objects for each group. Students complete three quick tests:

• push a book across a desk and observe friction;
• pull a toy car with a rubber band, changing the pull strength;
• move paper towards a magnet without touching it.

For each test, students record the action, the observed effect, the force type, and a labelled arrow diagram. They classify the forces as contact or non-contact and identify whether the forces appear balanced or unbalanced. Remind students that this is a qualitative investigation; they are comparing effects, not calculating exact forces.

5. 42–50 minutes – Group discussion and checking Return to the investigation discussion prompts. Groups share one observation and one force diagram. Ask: “How did the object’s motion or shape change?” and “What evidence suggests the forces were unbalanced?” Address the misconception that balanced forces mean “no forces”; explain that balanced forces can mean an object remains still or continues moving at a constant speed.

6. 50–56 minutes – Individual application Students complete the final questions on the forces investigation worksheet independently. They draw force diagrams for a book resting on a table and a ball slowing on grass, label the forces, and explain whether each situation is balanced or unbalanced. Circulate, checking arrow direction, labels and reasoning.

7. 56–60 minutes – Exit ticket Finish with the exit ticket questions. Students answer: “What is a force?”, “Give one contact and one non-contact example”, and “A stationary object is pushed and begins moving. Are the forces balanced or unbalanced? Explain.” Collect responses at the door and use them to group students for the next lesson.

Resources

• the force introduction, teaching and plenary deck
• the forces investigation worksheet
• the Forces Free-body Diagram Arrows
• One book, toy car, ruler, rubber band and magnet per group
• Small paper objects, such as paper clips or scraps of paper
• Desks or smooth floor space for testing movement
• Whiteboard and markers
• Optional force meters or spring balances
• Safety goggles for demonstrations involving stretched rubber bands

Assessment

• Observe group predictions, classifications and force diagrams during the investigation; question students about evidence and arrow direction.
• Check worksheet diagrams for correct labels, direction and balanced or unbalanced reasoning.
• Use the exit ticket to identify students needing reteaching about newtons, force types or balanced forces.

Differentiation

• Provide a word bank and partially completed diagrams for students needing support: push, pull, friction, gravity, magnetism, contact, non-contact, balanced and unbalanced.
• Pair students strategically and assign clear roles; allow students to explain observations orally before writing. Provide enlarged diagrams and uncluttered worksheet spacing for students with visual, literacy or fine-motor needs.
• For EAL/D learners, use gestures for push and pull, repeated sentence frames such as “The force is ___ because ___”, and labelled demonstrations.
• Extend confident students by asking them to draw two opposing arrows of different lengths and explain how the object’s motion would change, or to identify multiple forces acting on a moving car.