Science · Year 3 · Pushing and Pulling · Term 4

Introduction to Forces

Students will identify and describe various pushes and pulls encountered in everyday life.

• ACARA Content Descriptions
• AC9S4U03

About This Topic

Forces are pushes and pulls that change the motion or shape of objects. This topic introduces students to the distinction between contact forces (like kicking a ball or friction) and non-contact forces (like gravity and magnetism). This is a fundamental concept in the ACARA Physical Sciences strand for Year 4 (often introduced in Year 3), where students explore how forces can act at a distance. It encourages students to think about the invisible 'fields' that influence the world around them.

By experimenting with magnets and gravity, students see that physical touch isn't always necessary for movement. This topic is perfect for hands-on exploration and 'magic' demonstrations that are actually science. In the Australian context, we can look at how non-contact forces are used in technology, like the Maglev trains being discussed for future transport or the simple use of magnets in recycling centers. Students grasp this concept faster through structured discussion and peer explanation of their 'invisible force' observations.

Key Questions

1. Explain how a push differs from a pull.
2. Analyze how forces can change an object's motion or shape.
3. Compare the forces involved in kicking a ball versus lifting a book.

Learning Objectives

• Identify examples of pushes and pulls in everyday scenarios.
• Explain how a push differs from a pull using concrete examples.
• Analyze how forces can change an object's motion or shape.
• Compare the forces involved in kicking a ball versus lifting a book.

Before You Start

Observing and Describing Objects

Why: Students need to be able to observe and describe the properties of objects, such as their shape and how they move, before they can analyze forces acting upon them.

Basic Movement Concepts

Why: Familiarity with concepts like moving, stopping, and changing direction is foundational for understanding how forces cause these changes.

Key Vocabulary

Force	A push or a pull that can make an object move, stop moving, or change its shape.
Push	A force that moves something away from you.
Pull	A force that moves something towards you.
Motion	The act of moving or changing position.
Shape	The outline or form of an object.

Watch Out for These Misconceptions

Common Misconception

Forces only happen when something is moving.

What to Teach Instead

Forces are acting even on stationary objects (like gravity pulling you down while the chair pushes you up). Using a 'tug-of-war' analogy where no one is winning helps students see that forces can be balanced and still exist.

Common Misconception

Magnets only pull things.

What to Teach Instead

Magnets can also push (repel) if the same poles are facing each other. Letting students 'feel' the invisible push between two magnets is a powerful way to correct this through direct experience.

Active Learning Ideas

Stations Rotation: Force Finder

Stations include: pushing a toy car (contact), using a magnet to move a paperclip (non-contact), dropping a feather (non-contact), and stretching a rubber band (contact). Students classify each.

40 min·Small Groups

Inquiry Circle: Magnetic Maze

Students design a maze on a piece of cardboard. They must move a 'player' (a paperclip) through the maze using a magnet held underneath the board, demonstrating force through a solid.

30 min·Pairs

Think-Pair-Share: Gravity's Reach

If there was no gravity, what would happen to the ocean? Students think of three consequences, discuss with a partner, and share their most creative 'gravity-free' scenario.

15 min·Pairs

Real-World Connections

• Sports coaches use their understanding of forces to teach athletes how to kick a soccer ball with more power or throw a baseball faster by applying the correct pushes and pulls.
• Engineers design playground equipment like swings and slides, carefully considering the forces of gravity and friction to ensure safe and fun movement for children.
• Mechanics use wrenches to apply pushes and pulls to tighten or loosen bolts on a car, demonstrating how forces can change the state of an object.

Assessment Ideas

Exit Ticket

Provide students with a worksheet showing pictures of everyday actions (e.g., opening a door, riding a bike, squeezing a sponge). Ask them to label each action as a 'push' or 'pull' and briefly describe how the force changes the object's motion or shape.

Discussion Prompt

Ask students: 'Imagine you are pushing a toy car and then pulling it back to you. What is the difference between these two actions? How does each action affect the car's movement?' Encourage them to use the terms 'push' and 'pull' in their answers.

Quick Check

Hold up two objects, like a soft ball and a wooden block. Ask students to describe a push and a pull they could apply to each object. Then, ask: 'Which object do you think is easier to change the shape of, and why?'

Frequently Asked Questions

Is gravity a push or a pull?

Gravity is a pull. It is a non-contact force that pulls all objects with mass toward each other. On Earth, it pulls everything toward the center of the planet.

Can non-contact forces work through anything?

Magnetic forces can work through paper, plastic, and water, but they get weaker the further away the magnet is. Gravity works through everything and has an infinite range, though it also gets weaker with distance.

How can active learning help students understand non-contact forces?

Non-contact forces feel like 'magic' to children. Active learning, such as playing with magnets or conducting drop tests, allows students to 'test the magic' and discover the predictable rules that govern these invisible pulls and pushes.

How do we use non-contact forces in Australia?

We use magnetism in everything from fridge seals to the giant magnets in scrap metal yards. Gravity is essential for our hydroelectric power stations, where falling water turns turbines to make electricity.