Science // Energy

What happens when things collide

Ask questions and predict outcomes about the changes in energy that occur when objects collide

Ages
9 to 10
Type
Concept
Builds on
1 topic
Leads to
0 topics
Standards
1 code

Quick check

If the learner rolls two balls towards each other, can they predict what will happen when they hit and explain that energy transfers between them?

Ask this to see whether the topic is secure.

Topic // Mastery

What mastery looks like

What a learner can do once this topic is secure.
  • Predict the outcome of a collision based on the speeds and sizes of the objects
  • Explain that energy transfers from one object to another during a collision
  • Describe observable changes: one object speeds up, the other slows down, sound is produced

Topic // Map

Where this fits

What to learn first and what this topic opens up, with the reason for each link. Required links come first.
  • RequiredMust come first
  • HelpfulHelps, but not essential

Before this

1 topic
  • Speed and energyRequired

    Energy // Ages 9 to 10

    Must relate speed to energy before predicting energy changes in collisions

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What happens when things collide

Ages 9 to 10 // Concept

Leads to

0 topics

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Topic // Research-informed

Teaching notes

From the Marble Skill Taxonomy. These notes have not been validated in classrooms, so treat them as a starting point for your own judgement.

The approach

For ages 9–10: children ask questions and predict outcomes about the energy changes when objects collide. When objects collide, energy can transfer from one to another (often one speeds up while the other slows, though in a head-on crash both may slow or stop). Some energy also leaves the moving objects to the surroundings as sound and a little warming (and into squashing when objects deform), so it is redistributed, never destroyed. Keep everything qualitative and observational (NGSS 4-PS3-3): no momentum, no calculations, and emphasis on the energy change [curriculum wording omitted; reference 4-PS3-3] forces. The core predict-then-observe cycle and 'where did the energy go?' bookkeeping can run as a live screen simulation, with real marbles/physical collisions, or as reference/assessment companions; each is described below with its affordances and limits.

Common misconceptions

  • 'The energy just disappears when things stop after a crash' — the central energy-is-lost error; it transferred to the other object and to the surroundings (sound, warming), it didn't vanish.
  • Thinking only ONE object changes — children watch the target and ignore that the striker slowed down too.
  • Treating the sound of the collision as separate/irrelevant rather than as energy carried away from the moving objects.
  • Reasoning about which object 'wins' or 'pushes harder' (forces) instead of how the energy/speed changes — the NGSS clarification steers away from force talk here.
  • 'The bigger/heavier object always keeps moving and the small one always stops' — outcome depends on speeds and masses together; predict-then-test surfaces the surprises.

Useful representations

  • Two-ball collision: a moving ball striking a stationary one (giver slows/stops, receiver moves off) — the canonical transfer picture.
  • Before/after speed arrows on each object (long arrow = fast, short = slow) showing motion handed from one to the other.
  • A 'where did the energy go?' tally: into the other object (motion) + a bit to the surroundings (sound + slight warming).
  • Everyday anchors: snooker/pool break, bumper cars, a kicked ball striking another, skittles/bowling.

Teaching practices

  • Lead with predict-then-observe: before each collision the child predicts what will happen to BOTH objects ('which speeds up? which slows? will there be a sound?'), then runs it and compares — the gap is where the energy-transfer idea forms.
  • Use clean, watchable collisions — a rolling marble hitting a stationary one (Newton's-cradle / boules style), a fast ball hitting a slow one — so the transfer (giver slows, receiver speeds up) is directly visible.
  • Make the surroundings audible/visible: name the BANG and any warming as energy that left the moving objects — 'the click you hear is some of the energy leaving as sound' — which seeds conservation without the formal law.
  • Keep attention on energy/speed change, not force (the NGSS clarification is explicit): describe what happens to each object's motion and where the energy went, not how hard they pushed.
  • Vary the incoming speed and connect back to 'speed and energy': a faster striker transfers more (knocks the target further, louder click), reinforcing more-speed-more-energy.

Activities to try

  1. 1

    Collision lab: predict, run, and track where the energy goes

    Why it works: When things collide, energy doesn't disappear when the striker slows: it moves into the other object and some escapes to the surroundings as sound and a little warming. More incoming speed means more energy transferred.

    1. Choose incoming speed in a simulation, or release the same marble from different heights on a fixed ramp and observe its speed before a stationary target. Keep objects,surface and collision alignment unchanged for the speed comparison; explore a mass toggle separately.
    2. COMMIT a prediction before running: say what each object will do ('the red one will stop, the blue one will shoot off') AND predict whether there will be a sound.
    3. Observe both objects. In a nearly elastic,head-on equal-mass model with one target initially still, the striker nearly stops as the target moves off; with different masses or materials it may continue or rebound. Record the actual outcome rather than requiring every real collision to match one ideal case.
    4. Watch the energy bookkeeping: the striker's motion-bar shrinks as the target's grows, and a small 'surroundings' bar lights up for the sound and slight warming, so the total is visibly accounted for.
    5. Vary incoming speed while keeping the same objects,alignment and surface. A faster incoming object carries more kinetic energy; observe how much reaches target motion,sound,deformation or warming, rather than guaranteeing a particular loudness or travel distance.
  2. 2

    Watch real clean collisions and name where the energy went

    Why it works: When objects rebound,some energy remains as motion; when soft objects stop and deform,more of the initial motion energy becomes internal energy or deformation. Sound may carry some energy to the surroundings. Account for all these destinations rather than treating lost motion as destroyed energy.

    1. Roll one marble into a stationary one (Newton's-cradle / boules style) and watch the giver slow or stop while the receiver moves off.
    2. Use two identical balls of equal mass approaching head-on at equal speeds. Predict their motion before testing: hard,nearly elastic balls tend to rebound,while soft sticky clay balls may join and stop near the collision point. The materials and conditions matter; do not generalise this outcome to unequal masses.
    3. Close your eyes during the head-on crash and listen: what do you HEAR? Discuss what that sound tells you about where the energy went.
    4. Make a 'where did the energy go?' tally for each collision: any motion that remains or is passed to the other object + some to the surroundings (sound you hear, plus possible slight warming that may be too small to feel) + any squashing (deformation). For sticky clay balls that stop, most of the motion energy goes into squashing and warming rather than motion.
    5. Try everyday anchors — snooker/pool break, bumper cars, a kicked ball striking another, skittles/bowling — and describe the transfer each time.
  3. 3

    Predict outcomes and trace the energy (check/assess companion)

    Why it works: Learners can predict outcomes and name all the destinations of the energy, including the surroundings and deformation share, confirming they track energy rather than treat it as lost — the TOTAL energy, including the surroundings, is the same before and after; motion energy is shared between the objects and partly changed into sound, warming or squashing.

    1. Predict post-collision motion: for a given collision, choose what happens to ball B (and to the striker).
    2. Match 'energy went to →' with the destinations: the other object (motion) / sound / warming / squashing (deformation).
    3. Order a set of collisions using the same objects by how much energy the striker brings in (e.g. by incoming speed).
    4. Answer the counterexample: two identical marbles, one still; the moving one stops and the still one goes off at the same speed — did energy disappear, and where did it go?
    5. Answer: after any collision, is the total energy more, less, or the same as before, and where would you look for the 'missing' bit?

Topic // Standards

Curriculum standards

Codes for the curriculum statements this topic maps to. Each publisher owns its standard text.
Next Generation Science Standards (NGSS) K-5
4-PS3-3

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