ScienceGrade 10ages 15–16
♻️ Energy does not vanish
A ball rolls to a stop and it looks like its energy simply disappeared, but energy never vanishes — it changes form, usually into a small, hard-to-notice amount of heat spread through the surfaces that rubbed together.
Try this lesson freeNo card needed. The first lesson is free.
Download on the App StoreWhat your child learns
- As a ball rolls over a carpet, the carpet's fibres rub against it the whole way.
- Every rub jolts particles in both surfaces and makes them jiggle harder.
- Harder jiggling of particles is exactly what we call heat.
- It can be measured: the carpet and the ball are a little warmer once the motion has ended.
The mistake most kids make here
When something stops, the energy vanished into nowhere.
Try one question
When a rolling ball stops, the motion energy…
Where it went
- was erased into nowhere
- changed, mostly into heat and tiny shakes
- flew to the moon as a rock
Answer
changed, mostly into heat and tiny shakes — Yes. Friction does not destroy energy but spreads it among a great many particles.
How Maya teaches it
Your child tells Maya what they did in class. She teaches this topic at her desk, asks questions with tappable answers, and when the answer is wrong she explains why that answer was tempting instead of saying “try again”. She remembers what did not land and comes back to it.
Your child has it when they can: Say where the motion energy went when the ball stopped.
How to help at home
This misconception is understandable because the "missing" energy is real but invisible — a tiny rise in temperature spread across a carpet and a ball is not something you can see or feel by hand, so it looks like nothing happened to replace the motion.
Tonight, rub your palms together briskly for ten seconds and ask your child what they feel. Warmth. Ask where that warmth came from — it's the same idea as a rolling ball: motion energy became heat through rubbing (friction), it didn't disappear.
When your child says the energy "just went away," ask: "went away, or changed into something we can't easily see, like heat?" That question shifts the frame from disappearing to transforming, which is the actual rule — energy changes form, it is not created or destroyed.
A good sign she has it: she can explain that a car's brakes get hot when stopping, and connect that heat directly to the car's motion energy from a moment before, rather than treating the stop as energy loss.
Questions parents ask
- Where does the energy go when a moving object stops?
- It doesn't disappear — friction converts it mostly into heat, spread through the object and the surface it moved across, plus a little into sound. The total amount of energy stays the same; it just changes form.
- Why can't I feel the heat when a ball stops rolling?
- The heat is real but tiny and spread across a large surface (the floor and the ball), so the temperature rise is too small to notice by touch, even though it's measurable with sensitive instruments.
- Is this the same idea as a car's brakes getting hot?
- Yes — braking is a dramatic, easy-to-feel version of the same rule: the car's motion energy converts into heat in the brake pads, which is why brakes get noticeably warm after slowing a car down.
- How does Maya teach this differently from stating the law of conservation of energy?
- Maya asks the child to name where the energy went, rather than just accepting that it's "conserved," so the abstract law connects to a concrete answer — heat, sound, or another form — every time.
No card needed. The first lesson is free.
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Sources: Next Generation Science Standards