Students state the law of conservation of energy and use it to account for all the energy in a system, including energy transferred as heat and sound (AC9S9U05, node 1, a hinge node).
Load these into Waypoints Prepare: choose Load URL and paste the copied address, or download the file and import it. In Prepare, the worksheet's Teacher edition shows the answers; the student copy hides them.
Engage and Explore 8 min · Explain 10 min · Evaluate 3 min · Typical adds 3 min, Wider about 2 min
A concept tutorial for introducing or revising the idea. Set the width with ?width=minimum, typical (default) or wider. It builds on Year 8 energy (AC9S8U05) and comes before How much is useful? (efficiency).
The hinge: students who think energy is "used up" or "disappears" can't account for every output in an efficiency calculation and read Sankey diagrams as loss. The prediction and the braking question target it. Note the everyday meaning of "conserve energy" (save it) differs from the law.
Board notes: the coaster's total energy is set at the start and drawn as a dashed line; with friction (a steady force while moving) the heat and sound bar grows. On the high-friction track the car settles in a dip. Real coasters also lose energy to air resistance that grows with speed.
Replacing 'used up'. When a student says energy was used up, ask 'used up into what?' and wait for them to name heat or sound.
| What you will see | A question to ask | The fix |
|---|---|---|
| A student says the energy was used up. | Into what? Was anything warmer or louder afterwards? | It became heat and sound. It's still there, spread into the surroundings. |
| A student thinks friction destroys energy. | What did the red bar do when friction was on? | It grew: friction transforms kinetic energy into heat. The total stayed the same. |
| A student confuses the law with saving energy at home. | If you leave a light on, is energy destroyed? | No, it's transformed into light and heat. 'Saving energy' means using less of a useful supply, not stopping it being destroyed. |
One possible solution for each task. Other correct programs are fine.
Open task: any program that does what the step asks.
Open task: any program that does what the step asks.
Stretch: A ball dropped from 2 m bounces to 1.5 m. What fraction of its energy became heat and sound on the bounce? (A quarter: it has three quarters of its starting potential energy at the top of the bounce.)
Support: Give the equation as a frame: 'Total = potential + kinetic + heat and sound = … + … + … '.
For a student who has done the lesson and is still stuck. They paste it into an AI tool your school allows; it asks questions about this lesson's one idea and doesn't give answers. Students see it on the course recap page only through a link ending in ?coach=1: recap with coach prompts.
You are a patient science coach for a Year 9 student in Australia. Help me understand ONE idea only, from the lesson "Where does the energy go?". The idea: Conservation of energy — total energy is maintained in any system: I can state the law of conservation of energy and apply it to account for all energy in a system — including energy that is transferred as heat or sound rather than as useful output. What understanding looks like: - States the law of conservation of energy correctly - Explains that 'wasted' energy is transferred to the environment, not destroyed - Accounts for all energy outputs (useful + wasted) in a simple system Mistakes students often make here: - A student says the energy was used up. - A student thinks friction destroys energy. - A student confuses the law with saving energy at home. How to coach me (rules from the Waypoints Kit coach): - Ask me one short question at a time (2 to 4 sentences) and wait for my answer. Never give me the answer before you have heard my thinking, and don't hide the answer inside your question. - Start in Discover: ask me to explain the idea in my own words, or to predict what happens in a simple example. I can switch any time: "teach it back" (you play a beginner and I explain), "spot the flaw" (you show me an answer with one common mistake and I find it), or "check" (I explain, and you tell me what is solid and what to revisit). - If I am stuck or say "just tell me", ask what I think first, then give a small hint or a simpler example. Explain only after I have had a real go. - Stay in this idea: don't teach later ideas or add extra content. If I ask about something else, say it is for another lesson and bring me back. - After you help, ask me one reflective question, such as how I know my answer is right or what I would check. - Praise my effort and method, not my ability. - You can be wrong: if I rely on something you said, remind me to check it against my notes or the lesson. If you don't know, say so. - Use simple words. - Stop when I can explain the idea in my own words and get one new example right. Then tell me to go back to the lesson "Where does the energy go?".
A skateboarder has 2000 J at the top of a ramp and 1700 J of kinetic energy at the bottom. Where are the other 300 J?
Transferred as heat and sound because of friction and air resistance. The total is still 2000 J.
Next: How much is useful? (efficiency, node 2).
In class: drop balls of different kinds and measure bounce heights; feel a bike brake or sandpaper after rubbing.