Collision Contraptions

by | Nov 15, 2018

If you’ve ever doubted the natural engineering ability of you primary-aged students, just leave a large tub of dominoes in the cupboard of your classroom and wait for the next rainy day. They’ll be planning, building, testing and adjusting complex chain reactions designed for maximum destructive satisfaction in no time! The lesson below harnesses that creative energy in order to engage students in a literal “crash course” in physics. Students will build their own crazy contraptions to demonstrate how energy is transferred between colliding objects.

What I love about this lesson is its flexibility. There are a lot of scientific principles at play here, which makes for easy adaptation to suit your particular learning objectives. You could even expand it into an ongoing project, in which students continue to create new elements to their designs as they are introduced to the basics of forces and energy. Try combining all of the contraptions together into one large machine for maximum excitement!


This lesson has been adapted from Hawker Brownlow’s new series, STEM: Engaging Hands-On Challenges Using Everyday Materials.

Recommended Year Level: 4–5


Students will learn about energy transference by observing a “Newton’s cradle”. They will then build fun “contraptions” that utilise collisions to transfer energy.



  • Video: Newton’s Cradle
  • Rube Goldberg Machine videos, such as this music video from the band OK Go
  • Building materials, such as:
  • Things that roll: marbles, table tennis balls, golf balls, small toy cars
  • Things to make tracks: cardboard tubes, pipe insulation (split in half), funnels, metre rulers, dowels
  • Containers: cups, cans, plastic tubs, boxes
  • Things that can fall over: dominoes, blocks, small boxes, erasers
  • Things that provide structure: ice cream sticks, straws, pipe cleaners, paper plates, cardboard, index cards
  • Tools: scissors, different kinds of tape, string, rubber bands, staplers


Prior knowledge:

Students should be familiar with the concepts of potential energy (stored energy) and kinetic energy (energy in motion) and be able to give some examples.



Review the difference between kinetic energy and potential energy, and ask students for examples (e.g. A rubber band stretched on a finger has potential energy, which becomes kinetic energy when released; a book lying on the edge of a table has potential energy, which become kinetic energy if it falls off).


Show students the video of a Newton’s cradle. (A real one would also suffice, but may be difficult for the whole class to observe at the same time. The suggested video also has the advantage of being captured in slow motion.)


Ask students to focus on the ball on the right:

  • Does this ball have potential energy? (Yes, when someone lifts up the ball)
  • Does it have kinetic energy? (Yes, when the ball is released and swings down before crashing into the row of balls beside it.)
  • What happens to the first ball when it collides with the others? (It stops moving.)
  • Is kinetic energy still present? (Yes, it has moved along the chain of balls causing the ball on the left to fly up.)
  • How does the ball on the right get some kinetic energy back? (when the ball on the left swings down and crashes into the row of balls.)
  • Do you see any kinetic energy present in the middle balls? (You can see them colliding with each other, though it is not easy to observe when not in slow motion)

Tell students that when something with kinetic energy collides with another object, some, or most, of that energy is transferred to that object, which can cause it to move.


Note: Students might ask about whether the Newton’s cradle stops moving altogether. If so, where has the energy gone? The answer is that the kinetic energy of the balls is transformed into other forms of energy, such as the small amount of heat and sound generated by each collision, which eventually causes the balls to lose energy and stop moving.


Define the Problem and Plan:

Tell students that they will be building fun “contraptions” using the transfer of energy by collision. A contraption is a machine or a device that has lots of moving parts. Some contraptions (called Rube Goldberg machines) don’t have much of a purpose: they’re just fun to watch! If time allows, show some online examples. You may wish to pause at certain points of the video to see if students can identify examples of potential and kinetic energy, and how that energy is transferred.


Show students the materials available for this challenge. Have them brainstorm some ways to make items collide. They can try having items knock each other over, fall on top of each other, roll into each other or swing into each other.


Go over the Challenge Constraints for this challenge. Constraints tell engineers what they can and can’t do. Write the following constraints on the board:

  • Build a contraption that transfers kinetic energy through a collision in at least two ways.
  • Create a fun ending where the motion stops
  • Use only the materials given. You do not have to use all of the materials.


If you like, you can also give each individual or group a “budget” and place a “cost” on available materials. This will help them think more carefully about the materials they choose, rather than simply grabbing the first thing they see.


Students can then start planning their contraptions. During this time, they should spend some time handling the materials, and brainstorming ideas. They will then provide a sketch of their planned contraption and answer the following two questions:

  • What are the two (or more) ways you will transfer kinetic energy through a collision?
  • How will you connect the different parts so that the motion continues from the beginning to the end?


Build, Test, Improve

Allot time for students to build their contraptions. This may take 30–45 minutes, depending on the complexity of students’ designs.


Remind students that the engineering process is all about testing and improving their designs. They may make changes to their plans as many times as they like in the time available.


Circulate as students build and test their contraptions to observe and ask questions for formative evaluation.


Analyse and Evaluate

Have each group demonstrate their contraption for the class. Students should identify potential and kinetic energy and points of transfer. You may ask students to predict how the contraption will work before the demonstration.


Ask presenting students whether they had any trouble with making their contraption work (e.g. was there enough energy in the marble to make the golf ball move? How did you fix this?).


Writing Reflection

Have students reflect on their experiences in their books. Possible prompts include:

  • What materials did you use?
  • How did your contraption transfer energy?
  • Did you have to adjust or improve your contraption?
  • What patterns did you observe in the transfer of energy?
  • What was the hardest part of this activity?
  • What was your favourite part?

Mark O'Shea Mark O’Shea is a primary school teacher with a Bachelor of Arts and Education from Monash University. He loves designing creative, self-directed learning experiences for students of all ages, and joined Hawker Brownlow’s editorial team in 2017. Read more articles by Mark O'Shea

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