Principles of the Physical World: Senior Cycle Physics · 5th Year

Active learning ideas

Every Push Has a Push Back

Active learning turns Newton's Third Law from an abstract idea into something students can feel and see. Hands-on pushes and pulls make the equal-and-opposite relationship tangible, while group work lets students test predictions and debate outcomes together.

• NCCA Curriculum Specifications
• NCCA: Primary Curriculum - Science - Energy and Forces

• 25–45 min
• Pairs → Whole Class
• 4 activities

Activity 01

• 30 min · Pairs

Pairs Demo: Partner Push on Low-Friction Surfaces

Partners stand on skateboards or smooth floors and push against each other gently. They observe and measure backward motion with rulers or phones. Discuss which force is larger and switch roles to compare experiences.

What happens when you push against a wall?

Facilitation Tip

During Partner Push on Low-Friction Surfaces, remind students to start with gentle pushes so they can feel the equal recoil before increasing force.

What to look for

Present students with three scenarios: a book resting on a table, a person jumping off a dock, and a rocket launching. Ask them to identify the action-reaction force pairs for the jumping and rocket scenarios, and explain why the book scenario does not involve an action-reaction pair in the context of Newton's Third Law.

Activity 02

• 45 min · Small Groups

Small Groups: Balloon Rocket Races

Inflate balloons and attach to straws on strings stretched across the room. Release to propel forward; measure distances. Groups predict and test how balloon size affects speed, linking gas expulsion to rocket thrust.

Why does a boat move away when you step out of it?

Facilitation Tip

Before Balloon Rocket Races, have groups plan one variable to test, such as balloon size or track length, to focus their investigation.

What to look for

Pose the question: 'If action and reaction forces are equal and opposite, why does a heavy truck cause more damage in a collision than a small car?' Guide students to discuss how forces act on different objects and how mass and acceleration (Newton's Second Law) influence the outcome.

Activity 03

• 35 min · Whole Class

Whole Class: Cart and Fan Propulsion

Place a battery-powered fan on a low-friction cart facing backward. Turn on to observe forward motion. Class votes on predictions, then measures acceleration with timers and discusses action-reaction on air versus cart.

How does a rocket move into space?

Facilitation Tip

When running Cart and Fan Propulsion, ask students to predict the cart’s motion before turning on the fan to make their observations more intentional.

What to look for

On a slip of paper, ask students to draw a simple diagram illustrating one action-reaction force pair (e.g., walking, a bird flying). They should label both forces and briefly state Newton's Third Law in their own words.

Activity 04

• 25 min · Individual

Individual: Force Pair Sketches

Students sketch free-body diagrams for scenarios like jumping off a boat or firing a rocket. Pair up to critique, then share corrections with class. Focus on labeling equal/opposite forces clearly.

What happens when you push against a wall?

Facilitation Tip

For Force Pair Sketches, provide a rubric with labels for action, reaction, and objects so students know exactly what to include.

What to look for

Present students with three scenarios: a book resting on a table, a person jumping off a dock, and a rocket launching. Ask them to identify the action-reaction force pairs for the jumping and rocket scenarios, and explain why the book scenario does not involve an action-reaction pair in the context of Newton's Third Law.

A few notes on teaching this unit

Start with a quick demo where you push against a wall and ask students to feel the push back. This anchors the concept in their bodies before moving to abstract examples. Avoid rushing to equations; let students observe patterns first. Research shows that concrete experiences followed by guided reflection build stronger mental models than lectures alone.

Students will confidently identify action-reaction pairs in real situations, measure forces with simple tools, and explain why forces don’t cancel out when they act on separate objects. They’ll use diagrams and language to show that pushes always come in pairs.

---

Watch Out for These Misconceptions

• During Partner Push on Low-Friction Surfaces, students may argue that their push is stronger than their partner’s push back.

  Have partners use spring scales to measure both pushes simultaneously, then compare readings to show the forces are equal in magnitude and opposite in direction.

• During Partner Push on Low-Friction Surfaces, students may claim that objects only push back if they are moving.

  Have students push against a stationary wall and discuss how the wall exerts an equal reaction force even though it does not move.

• During Cart and Fan Propulsion, students may think the action-reaction forces cancel out and prevent motion.

  Ask students to observe the cart’s motion and explain that the forces act on different objects—the fan pushes air down, while the air pushes the cart up—so motion occurs.