What Happens When Things Bump?

Active learning invites students to see the push and pull of forces firsthand, making abstract ideas about motion concrete. When students roll toy cars or swing pendulums, they connect classroom physics to real-world collisions, building lasting understanding through movement and observation.

• 5th Year
• Principles of the Physical World: Senior Cycle Physics
• 4 activities
• 30 min–45 min

Learning Objectives

1. Compare the change in velocity of two toy cars after a head-on collision, given initial conditions.
2. Explain how the mass of colliding objects affects the outcome of a collision, using Newton's laws.
3. Analyze the transfer of motion between a moving object and a stationary object during a collision.
4. Predict the final state of motion for two objects after a collision, based on their initial states.

Experiential Learning

⏱ 45 min·Small Groups

Toy Car Crash Tracks: Ramp Collisions

Build ramps with toy cars of different masses. Release one car to collide with a stationary car at the bottom, measure distances traveled post-collision using tape measures. Repeat with speed variations, record data on charts.

Prepare & details

What happens when two toy cars crash into each other?

Facilitation Tip: During Toy Car Crash Tracks, remind students to measure the ramp height and track length precisely so they can compare speeds before and after collisions.

Setup: Varies; may include outdoor space, lab, or community setting

Materials: Experience setup materials, Reflection journal with prompts, Observation worksheet, Connection-to-content framework

• Apply
• Analyze
• Evaluate
• Self-Awareness
• Self-Management
• Social Awareness

Experiential Learning

⏱ 30 min·Pairs

Marble Run Collisions: Chain Reactions

Set up a straight track with gates for marbles. Launch one marble to hit a line of stationary ones, observe transfer along the chain. Vary marble sizes, note which moves farthest, discuss patterns.

Prepare & details

How does a billiard ball move after hitting another ball?

Facilitation Tip: In Marble Run Collisions, challenge students to design a chain reaction with at least three marbles, encouraging them to adjust spacing and angles to achieve a smooth flow.

Setup: Varies; may include outdoor space, lab, or community setting

Materials: Experience setup materials, Reflection journal with prompts, Observation worksheet, Connection-to-content framework

• Apply
• Analyze
• Evaluate
• Self-Awareness
• Self-Management
• Social Awareness

Experiential Learning

⏱ 35 min·Small Groups

Pendulum Bumps: Swing Transfers

Suspend strings with bobs of equal mass. Release one pendulum to strike another at rest, measure swing heights before and after. Test unequal masses, predict and verify outcomes.

Prepare & details

Can a moving object make a still object move?

Facilitation Tip: For Pendulum Bumps, have students release the pendulum from the same height each time to ensure consistent energy transfer for fair comparisons.

Setup: Varies; may include outdoor space, lab, or community setting

Materials: Experience setup materials, Reflection journal with prompts, Observation worksheet, Connection-to-content framework

• Apply
• Analyze
• Evaluate
• Self-Awareness
• Self-Management
• Social Awareness

Experiential Learning

⏱ 40 min·Whole Class

Billiard Table Mini-Games: Angle Shots

Use a low-friction table or felt with balls. Practice straight and angled shots, track paths with string lines. Groups compete to predict stationary ball paths accurately.

Prepare & details

What happens when two toy cars crash into each other?

Facilitation Tip: When running Billiard Table Mini-Games, provide protractors and rulers so students can accurately measure angles and distances before and after shots.

Setup: Varies; may include outdoor space, lab, or community setting

Materials: Experience setup materials, Reflection journal with prompts, Observation worksheet, Connection-to-content framework

• Apply
• Analyze
• Evaluate
• Self-Awareness
• Self-Management
• Social Awareness

Teaching This Topic

Start with hands-on trials to build intuition before introducing formulas, as research shows concrete experiences anchor abstract concepts. Avoid rushing to conclusions; let students test ideas multiple times to refine their models. Encourage peer discussion to surface misconceptions early, using their experiments as evidence to correct thinking.

What to Expect

Students will describe how momentum transfers between objects, noting changes in speed and direction after collisions. They will use evidence from experiments to explain why some collisions look different from others.

Watch Out for These Misconceptions

Common Misconception

During Toy Car Crash Tracks, watch for students who assume the larger car always stops the smaller one completely.

What to Teach Instead

Ask students to adjust the ramp height to change the speed of the larger car and observe if the smaller car still moves forward after the collision, using their data to challenge this idea.

Common Misconception

During Pendulum Bumps, watch for students who think all motion is destroyed in a crash.

What to Teach Instead

Have students attach a piece of clay to the pendulum bob and observe the deformation while tracing the motion of the second pendulum after the bump, noting that motion continues even if objects deform.

Common Misconception

During Billiard Table Mini-Games, watch for students who think direction never changes in head-on bumps.

What to Teach Instead

Ask students to predict and test what happens when two balls of equal mass collide head-on, then have them adjust to unequal masses to observe partial transfers and directional changes.

Assessment Ideas

Exit Ticket

After Toy Car Crash Tracks, provide students with a scenario: 'A 2kg cart moving at 5 m/s collides with a stationary 1kg cart. Describe what happens to the motion of both carts immediately after the collision, considering their masses and initial speeds.' Ask them to use their experimental data to justify their answer.

Quick Check

During Marble Run Collisions, set up two marbles with different masses. Ask students to predict what will happen when the heavier marble collides with the lighter, stationary marble. Then, perform the collision and ask students to describe the observed changes in motion, relating it to their prediction.

Discussion Prompt

After Billiard Table Mini-Games, pose the question: 'Imagine a large truck hitting a small car. Based on what we've learned about collisions, what do you predict will happen to the motion of both vehicles? How does Newton's third law apply here?' Facilitate a class discussion comparing predictions and observations.

Extensions & Scaffolding

• Challenge students to design a collision setup where a light marble knocks a heavy block off a ledge by adjusting the ramp angle and starting position.
• Scaffolding: Provide pre-labeled diagrams of the collision setup for students to trace forces and momentum arrows during Marble Run Collisions.
• Deeper exploration: Introduce a slow-motion video analysis of real-world collisions, like sports tackles or car crashes, to connect classroom experiments to safety engineering.

Key Vocabulary

Collision	An event in which two or more bodies exert forces on each other over a relatively short time.
Momentum	A measure of an object's motion, calculated as mass multiplied by velocity. It is a vector quantity.
Conservation of Momentum	The principle stating that the total momentum of a closed system remains constant, even when objects within the system collide.
Action-Reaction Force	For every action, there is an equal and opposite reaction, as described by Newton's third law. These forces occur simultaneously during a collision.