A Primary 6 PSLE Science pupil drops a rubber ball from a marked height of 100 cm. After striking the floor, it rises only to about 70 cm. The child says, “The ball used up its energy and some energy disappeared.” The change in bounce height is observable, but the explanation needs correction: energy is converted and transferred, including into sound and thermal energy during the collision, rather than simply ceasing to exist.
This everyday question connects gravitational potential energy, kinetic energy, elastic effects, sound and heat in a way that helps a pupil reason rather than recite. The sequence matters: as the ball falls, gravitational potential energy decreases while kinetic energy increases; the collision briefly deforms the ball and transfers energy; then the rebound carries the ball upward again.
For Petain Road families in the Jalan Besar area, weekday-versus-weekend tuition should be selected based on that missing link. A weekday lesson can correct the statement that energy vanished, while weekend time can support controlled comparisons of bounce heights and different surfaces. Both should end with an unfamiliar energy-conversion question answered without prompts.
eduKateSG · Primary 6 PSLE Science · Petain Road
A lower bounce does not mean energy was destroyed. Some energy was transferred into sound, heat and deformation rather than returning to the ball’s useful upward motion.
Full chapter index
1. Diagnose the meaning of ‘energy disappeared’ · 2. Describe energy before the ball is released · 3. Explain the collision with the floor and momentary deformation · 4. Follow kinetic and gravitational energy on the rebound · 5. Read an illustrative three-bounce height record · 6. Design a fair bounce comparison with safe equipment · 7. Use a weekday lesson to correct the energy explanation quickly · 8. Use a weekend lesson for several cause-and-effect comparisons · 9. Write an open-ended PSLE answer tied to the observed height · 10. Retest with a different object and review the parent decision
1. Diagnose the meaning of ‘energy disappeared’
The pupil sees that the rebound height is smaller than the release height. That observation is real. The phrase “energy disappeared” is not a satisfactory scientific explanation because it ignores transfers and conversions that occurred when the ball hit the floor and interacted with surrounding air.
Ask what happens at the collision: there may be a sound, the ball and floor deform for a brief time, and a small amount of energy is transferred into thermal motion. Not all of the ball’s energy becomes upward motion again. The ball can therefore rebound to a lower peak even though energy has not been destroyed.
The first tutoring task is to distinguish a reduced useful mechanical energy in the rebound from a loss of total energy from the wider system. Do not ask the pupil to memorise complicated formulas before they can describe the causal sequence.
2. Describe energy before the ball is released
When a ball is held above the floor, it has gravitational potential energy associated with its position in Earth’s gravitational field. The greater its height relative to a chosen reference level, the greater this gravitational potential energy for the same ball under the same conditions.
Release the ball from rest without adding a push. Gravity causes it to accelerate downward. As it falls, gravitational potential energy is converted into kinetic energy of movement. Air resistance also transfers some energy to the surrounding air. A primary-level explanation may focus on the main gravitational and kinetic forms without doing advanced calculations.
Emphasise what the comparison controls. Using the same ball and release height lets the learner reason about the changes. Comparing a heavy basketball dropped from a different height with a small rubber ball is a different experiment with more variables.
3. Explain the collision with the floor and momentary deformation
Just before impact, the falling ball has substantial kinetic energy. During the impact, a rubber ball typically changes shape briefly and then recovers much of that shape as it rebounds. Elastic behaviour enables some stored energy during deformation to return to upward movement, but the collision is not perfectly efficient.
Energy is transferred to the ball and floor as heat, and to the surroundings as sound and vibrations. The small temperature changes are usually not obvious to touch in an ordinary gentle bounce, so do not claim a child measured them by hand. Their existence is supported by physical understanding, while the sound can often be heard directly.
A pupil who claims “the floor gives the ball brand-new energy” needs a different correction: the interaction allows energy from the moving and deformed system to drive the rebound. The floor affects the bounce, but this is not creation of energy from nothing.
4. Follow kinetic and gravitational energy on the rebound
Immediately after the ball leaves the floor, it is moving upward with kinetic energy. As it rises, its speed generally decreases while gravitational potential energy increases. At the top of the bounce the ball is momentarily at rest before falling again. Because some energy has been transferred into less recoverable forms during the previous collision and flight, the rebound peak is often lower than the original release height.
This explanation needs conditions. A ball deliberately struck upward by a person could rise higher because the person adds energy. A powered device could also change the outcome. The standard teaching case concerns an ordinary unpowered rubber ball dropped without an additional push onto a stationary floor.
Ask the learner to label energy at four positions: held high, falling, touching the floor and rising. Correct arrows and position descriptions are more useful than copying the words potential and kinetic as an unconnected list.
5. Read an illustrative three-bounce height record
The following is fictional teaching data, not a measured experiment conducted on Petain Road or a guaranteed performance figure for any rubber ball. Imagine the same ball released from rest at 100 cm above a firm, level surface. It reaches a peak height of 70 cm after the first bounce, 49 cm after the second, and 34 cm after the third. The illustrative peak heights decrease.
The child should report the trend before explaining it: each successive peak is lower in the given table. The scientific explanation is that the ball–floor system transfers some energy into sound, heat and other forms during each impact, and air interactions also affect motion. The remaining energy available for upward movement is lower after each bounce.
Do not claim that the exact proportion of rebound height must be identical for all balls or all surfaces. Real outcomes depend on ball material, inflation, temperature, floor properties and method. The table supports a qualitative energy-transfer explanation.
| Stage in fictional record | Peak height above floor | Supported observation |
|---|---|---|
| Initial release | 100 cm | Starting reference height |
| Peak after first impact | 70 cm | First rebound below release |
| Peak after second impact | 49 cm | Second peak below first |
| Peak after third impact | 34 cm | Third peak below second |
| Alternative with an extra upward push | Not provided | Cannot predict from the simple record |
6. Design a fair bounce comparison with safe equipment
For a classroom investigation, choose one suitable rubber ball and one stable floor surface. Release it from the same measured height without pushing or spinning it. Use the same method to observe each peak height, perhaps with a fixed ruler or video under teacher supervision. Repeat trials and record variation rather than adjusting readings to create a perfectly smooth decline.
If testing different surfaces, deliberately change only the landing surface and keep the ball, release height and measurement procedure similar. A soft mat may absorb and deform differently from a firm floor, but the precise rebound heights cannot be inferred without data. A question comparing two surfaces should describe their properties and measurements.
Do not conduct bounce tests against conserved Petain Road shophouse façades, tiled surfaces, windows or fragile property. A safe supervised school area or a paper-record exercise is enough. The educational objective is reasoning, not the largest or loudest possible impact.
7. Use a weekday lesson to correct the energy explanation quickly
If a child loses marks by writing “energy disappears after a bounce”, a weekday Science session can begin with that sentence and the 100 cm-to-70 cm illustration. Ask what was heard, what physically changed at impact and why those effects matter for the energy available to the ball’s rebound.
The child should write a short corrected response that states energy was converted and transferred, including sound and heat, then explain the lower height. Remove the ball picture and ask about a toy car slowing on a rough surface. The same distinction appears: energy is transferred into other forms; it is not simply destroyed.
A focused session is valuable when it leaves enough energy for thought and a later independent retest. Parents should choose the actual teaching venue and time with travel, meals, schoolwork and sleep in mind.
8. Use a weekend lesson for several cause-and-effect comparisons
A weekend tutorial may provide time for comparing the same ball on firm and soft surfaces, different release heights, and a ball that is briefly pushed upward after contact. Each is a separate question; if several factors change at once, a causal conclusion becomes unreliable. The learner should explain the role of each condition before interpreting any graph.
In a three-pupil group, rotate energy-pathway explainer, variable checker and data interpreter. After the shared activity, give each pupil a different unseen case. One child might explain an elastic ball, another a foam ball and another a rolling toy slowing down. A tutor needs individual written evidence rather than agreement from the whole group.
Do not make the lesson a secondary-school exercise in coefficients of restitution unless that extension is clearly appropriate and separate from PSLE requirements. The core is accurate forms, directions of transfer and supported explanations.
9. Write an open-ended PSLE answer tied to the observed height
Question: “A rubber ball dropped from 100 cm rebounds to only 70 cm. Explain why it does not return to the starting height.” A strong response is: “As the ball falls, gravitational potential energy is converted into kinetic energy. During the collision with the floor, some energy is transferred as sound and heat and through deformation. Less energy is available to raise the ball after the bounce, so its rebound height is lower.”
An incomplete answer simply says “because of gravity”. Gravity affects both descent and ascent, but the lower rebound also needs an explanation of the energy transfer at and around the collision. Saying “the missing energy vanishes” is likewise incorrect.
A good student can distinguish the energy of the ball from the energy of the wider system. Total energy is conserved, while the portion that returns as the ball’s useful upward motion becomes smaller after a typical bounce.
10. Retest with a different object and review the parent decision
Two or three days later, show a spring toy that is compressed and then released, launching a small lightweight object upward. Ask where energy is stored initially and how it becomes kinetic energy and then gravitational potential energy as the object rises. This changes the original gravitational starting point while preserving the principle that energy changes form.
Next provide a short table comparing the same ball released from one height onto two surfaces. Ask why one rebound peak might differ and which variables must remain unchanged to make the comparison fair. The child should not assume every soft surface produces an exact fraction of the firm-floor bounce without data.
Did the ball’s energy get destroyed? No, energy is transferred and converted. Are height percentages universal? No. Is weekend tuition better? Only if more varied comparisons are needed and the learner remains attentive. Does three-pupil tutoring suit quiet learners? Yes when each completes their own unseen explanation. Petain Road names the reader area, not an eduKate teaching venue or confirmed vacancy.
Independent changed-question check: A compressed spring toy launches a small object upward. Explain where energy begins and how it changes as the object rises, then state why this is not the same starting condition as a freely dropped ball.
Collect the pupil’s answer without prompts, then compare it with the original misconception and plan the next teaching step.
Weekday versus weekend parent decision table
| Parent decision | Weekday Science tuition | Weekend Science tuition |
|---|---|---|
| Fresh misconception | Correct ‘energy vanished’ promptly | Compare rebound height, material and energy paths |
| First lesson | Falling → impact → rising sequence | Controlled surface and ball comparisons |
| Two-day retest | Compressed spring launches object | Unseen bounce-height results |
| Evidence of learning | Explains transfers and lower peak | No invented constant bounce percentages |
Official syllabus, further reading and eduKate Science resources
Curriculum and learning: MOE 2023 Primary Science Syllabus · Primary Science Tuition Singapore · weekday–weekend learning rhythm · three-pupil learning standard · parent–student consultation. Follow the child’s actual school chapter and applicable Standard or Foundation requirements.
Science references: University of Illinois Physics Van: Ball Bounce Height · Open Source Physics Singapore: Bouncing Object Study · URA Petain Road conservation reference. The diagrams and numerical teaching examples here do not represent local measurements or confirmed tuition activities.
Different Primary 6 PSLE Science teaching cases: Desker Road · Jalan Berseh · Syed Alwi Road. These varied cases can support retrieval practice without copying model answers.
Other Petain Road Science levels: Primary 3 Science · Primary 4 Science · Primary 5 Science.
Petain Road is a named reader area in the Jalan Besar Conservation Area, not a verified eduKate teaching address, a current vacancy or a promise of results. Confirm actual tutorial locations, fees and schedules before choosing a class.