MS-PS3-2: Modeling How Arrangement Changes Stored Potential Energy
In plain English: MS-PS3-2 is the NGSS middle school performance expectation that asks students to develop a model showing that when two objects that push or pull on each other without touching change position, the system stores a different amount of potential energy. Students compare more and less, not calculated values, for gravity, magnets and static charge. It is usually taught in grade 6, 7 or 8 physical science.
Develop a model to describe that when the arrangement of objects interacting at a distance changes, different amounts of potential energy are stored in the system.
Clarification Statement: Emphasis is on relative amounts of potential energy, not on calculations of potential energy. Examples of objects within systems interacting at varying distances could include: the Earth and either a roller coaster cart at varying positions on a hill or objects at varying heights on shelves, changing the direction/orientation of a magnet, and a balloon with static electrical charge being brought closer to a classmate's hair. Examples of models could include representations, diagrams, pictures, and written descriptions of systems.
Assessment Boundary: Assessment is limited to two objects and electric, magnetic, and gravitational interactions.
Next Generation Science Standards · Disciplinary Core Idea: Energy · Official standard
Students build models that show where energy is stored when two objects pull or push on each other without touching. A system is the set of objects we choose to study. Potential energy is energy stored in a system because of how its objects are arranged, that is, where they are and which way they face. Students compare three kinds of interaction at a distance (a push or pull that acts without contact): gravity between Earth and an object, magnetic forces between two magnets, and electric forces between a charged balloon and hair. They draw labeled pictures, energy bar models (bars that show more or less energy, with no numbers) and written descriptions, then use simple invented data to test their models.
The NGSS Clarification Statement says: "Emphasis is on relative amounts of potential energy, not on calculations of potential energy. Examples of objects within systems interacting at varying distances could include: the Earth and either a roller coaster cart at varying positions on a hill or objects at varying heights on shelves, changing the direction/orientation of a magnet, and a balloon with static electrical charge being brought closer to a classmate's hair. Examples of models could include representations, diagrams, pictures, and written descriptions of systems." The Assessment Boundary says: "Assessment is limited to two objects and electric, magnetic, and gravitational interactions." So every system on this page has exactly two objects, and no one computes an amount of energy. All data sets are invented for teaching.
Learning Objectives
By the end of this lesson, students will be able to:
Identify the two objects in a system that interact at a distance, and name the interaction as gravitational, magnetic or electric
Develop a model (labeled drawing, energy bar model or written description) that shows more or less stored potential energy for different arrangements of the same two objects
Use the rule for attracting and repelling pairs to predict whether moving the objects apart, moving them together or turning a magnet around stores more or less energy
Use simple data, such as how far an object moves once released, as evidence for which arrangement stored more energy
Critique a model and fix it, for example a model that places the stored energy inside one object instead of in the system
Prior Knowledge Required
Students should already be comfortable with:
Gravity pulls objects down toward Earth 5-PS2-1
The faster an object moves, the more energy it has 4-PS3-1
Magnets attract or repel, and like poles push apart
Reading a simple data table and putting values in order
Hold up a can of soup and point to a low shelf and a high shelf in the room. Do not drop anything. Ask students to think, then sketch.
Warm-Up Prompt
"The same can of soup could sit on a shelf near the floor or on a shelf near the ceiling. If it fell from each one, which fall would make a bigger dent in a cardboard box below? Before it falls, where is that energy? Draw a quick picture and label it."
Collect two or three sketches. Many students write that the energy is "in the can." Do not correct this yet. Tell students that today they will find out whether the energy belongs to the can alone or to something bigger.
Direct Instruction15 minutes
Key words. A system is the set of objects we choose to study. Two objects interact at a distance when one pushes or pulls on the other without touching it, as Earth pulls on a falling ball. Potential energy is energy stored in the system because of the arrangement of its objects. The energy belongs to the pair, not to one object. To attract is to pull together; to repel is to push apart. A model is a drawing, diagram or description that shows how a system works. An energy bar model uses bars of different heights to show more or less energy, with no numbers.
The rule. To change the arrangement, something has to push or pull against the interaction, and that adds energy to the system or takes it away.
For a pair that attracts (Earth and a cart, a north pole facing a south pole, a charged balloon and hair), moving the objects farther apart stores more energy.
For a pair that repels (two north poles, two balloons rubbed on hair), moving the objects closer together stores more energy.
The evidence is what the system can do when you let go: more stored energy lets the objects move faster or farther. Use Diagram 1 for the roller coaster and Diagram 2 for the magnets.
Earth and a roller coaster cart at three positions
A cart sits at the top of the first hill (A), halfway down (B) and at the bottom (C). The system is Earth and the cart; they attract.
Result: Model: A stores the most energy, B less, C the least. The cart is farthest from Earth at A, and for an attracting pair, farther apart means more stored energy. Evidence: a cart let go at A can roll down and over a smaller hill, while a cart let go at C barely moves.
Earth and the same object on three shelves
The same can of soup is placed on shelves 30 cm, 90 cm and 150 cm above the floor. The system is Earth and the can.
Result: Model: the 150 cm shelf stores the most, then 90 cm, then 30 cm. Lifting the can from a lower shelf to a higher one adds energy to the Earth-can system. The energy is not inside the can: it depends on where the can is compared with Earth.
Turning one magnet around
Two ceramic bar magnets lie 1 cm apart on a table. First a north pole faces a south pole. Then one magnet is turned around so that north faces north, still 1 cm apart.
Result: Model: the north-north arrangement stores more energy. When released, the north-north pair slides apart on its own, and the north-south pair can only snap together. Turning the magnet around changed the arrangement, so it changed the stored energy, even though the gap stayed 1 cm.
A charged balloon brought toward a classmate's hair
A latex-free balloon is rubbed on a wool cloth, which gives it a static charge (extra electric charge that stays put). It is held 30 cm, then 10 cm, then 2 cm from a volunteer's hair. The hair rises more as the balloon gets closer.
Result: Model: the balloon and the hair attract, so the stored energy is largest at 30 cm and smallest at 2 cm. As the gap shrinks, some stored energy goes into moving the hair. Pulling the balloon away again stores energy, and your hand supplies it.
Two charged balloons (a repelling pair)
Two balloons are each rubbed on the same wool cloth, so they carry the same kind of charge. They hang on threads and are pushed from 20 cm apart to 5 cm apart.
Result: Model: they repel, so the 5 cm arrangement stores more energy than the 20 cm one. Evidence: let go at 5 cm and they swing apart quickly. Compare with the balloon and hair: the same move (closer together) has the opposite effect, because that pair attracts.
After each example, ask: "What are the two objects? Do they attract or repel? Which arrangement stores more, and what is your evidence?" Point out that no example uses numbers for the energy. The models compare more and less, which is what this standard asks for.
Guided Practice10-15 minutes
Show the invented data below from a teacher test. Two toy cars each have a ceramic ring magnet taped to the front, with like poles facing. The teacher holds the cars at a starting gap, lets go, and measures how far the two cars rolled in total before they stopped. The system is the two magnet cars.
Guided practice data (invented): magnet cars with like poles facing
Starting gap (cm)
1
2
3
4
5
Total distance rolled (cm)
48
22
11
6
3
Name the two objects and the interaction. Do they attract or repel?
Rank the five starting gaps from most stored energy to least. Which column of the table is your evidence?
Draw an energy bar model with one bar per gap. Make the bars taller or shorter to match your ranking, with no numbers on the bars.
Write one sentence: "When the like poles start closer together, the system stores ___ energy, because ___."
Expected reasoning: the 1 cm start stores the most and the 5 cm start the least, because the cars rolled farthest from 1 cm. Ask: "What did the teacher keep the same in every trial, and why does that make the data fair evidence?" (The same cars, magnets, floor and way of letting go.)
Independent Practice10 minutes
Each student builds a three-panel model of a new system: a sheet of plastic wrap that has been rubbed with a wool cloth, held 25 cm, 12 cm and 3 cm above a tray of tiny tissue paper bits. The charged plastic and the tissue attract. In each panel, students draw the two objects, an arrow showing the pull on the tissue, and an energy bar. Under the panels they write three sentences: what the system is, which panel stores the most energy, and what happens to that energy as the gap shrinks.
Collect the models. Check that the tallest bar is at 25 cm, that students treat the tissue bits in the tray as one object, and that the description says the energy belongs to the plastic-tissue system.
Closure5 minutes
Exit ticket: "A refrigerator magnet is held 4 cm from a steel door, then pulled back to 8 cm. Did the stored energy of the magnet-door system go up or go down? Who or what supplied the change?" (Up: they attract, so pulling them apart stores more energy, and the hand supplied it.) Return to the warm-up sketches and ask students to relabel the energy as belonging to the Earth-can system.
Differentiation Strategies
For Struggling Students
Give a sentence frame for every model: "The two objects are ___ and ___. They ___ (attract or repel). The arrangement with more stored energy is ___ because ___."
Start with gravity only (shelves and the roller coaster), then add magnets, then static charge
Provide an attract and repel reference card with two pictures: arrows pointing together (farther apart stores more) and arrows pointing apart (closer together stores more)
For Advanced Students
Ask students to explain why turning one magnet around makes a big difference at 1 cm but almost none at 30 cm
Have students add a second model for the magnet cars with one car turned around, and predict how the five bars would change
Ask students to write a model for a system they choose, such as a kite stuck high in a tree, and trade it with a partner for critique
Assessment Guidance
What to Look For
Check that every model names exactly two objects and the kind of interaction. Look for bar models whose order matches the rule (attracting pair: farther apart stores more; repelling pair: closer together stores more) and for evidence drawn from what the objects do when released. Listen for students who place the energy inside one object, who think a resting object has no stored energy, or who use "closer means more" for every pair.
02
Classroom Activities
3 Activities
1
Marble Coaster Hill
20 minGroups of 3
Groups tape a length of split foam pipe insulation into a U-shaped track: a tall starting hill, a dip and a second hill. They release a marble from three heights on the first hill and measure the highest point it reaches on the second hill. The system is Earth and the marble.
Procedure
Tape one end of the track to a wall or a stack of books so the first hill can be 60 cm tall, and curve the track along the floor and up a second support.
Release the marble from rest (do not push it) at 20 cm, 40 cm and 60 cm above the floor. One student watches the second hill and marks the highest point the marble reaches with a sticky note.
Measure each mark's height above the floor with a meter stick. Repeat each start twice.
Safety: roll marbles on the floor only, and pick up every marble right away so no one slips.
Sample Data (invented)
Release height 20 cm: the marble climbs to 16 cm. Release height 40 cm: 33 cm. Release height 60 cm: 49 cm.
Build the Model
Draw the track with the marble at its three starting points. Next to the drawing, draw an energy bar for the Earth-marble system at each start, with no numbers. Write two sentences explaining your bars with the data as evidence.
Discussion Questions
The higher start always gave the higher climb. What does that tell you about the energy stored at each start?
Every climb was lower than its starting height. Where could the missing energy have gone? (Think about the rubbing between the marble and the foam, and the sound.)
Could the marble ever climb higher than where it started, without a push? Use your model to explain.
Modification for Distance Learning
Students build a track from a cardboard tube cut in half or a folded file folder at home, or they analyze the sample data and post their bar models to the class board.
2
Magnet Flip Lab
20 minPairs
Pairs test how the arrangement of two ceramic bar magnets changes what the magnets can do on their own. They change both the gap and the orientation (which way one magnet faces), then model the stored energy of the two-magnet system.
Procedure
Lay a sheet of paper on the table and mark lines 1, 2, 4 and 8 cm from one edge. Hold magnet A still at the edge.
Orientation 1, north facing north: place magnet B at each line, let go, and measure how far it slides away.
Orientation 2, north facing south: turn magnet B around, place it at each line, let go, and record whether it slides to magnet A or stays put.
Safety: use ceramic magnets only, keep them away from phones, laptops and anyone with a medical device, and keep fingers clear when magnets snap together.
Sample Data (invented)
North facing north: from 1 cm, B slid away 14 cm; from 2 cm, 6 cm; from 4 cm, 1 cm; from 8 cm, it did not move. North facing south: from 1 cm and 2 cm, B snapped to A; from 4 cm, B slid slowly to A; from 8 cm, it did not move.
Build the Model
Make a two-row bar model, one row per orientation, with a bar for each gap. For north facing north, the tallest bar goes at 1 cm. For north facing south, the tallest bar goes at 8 cm. Add one sentence explaining why the two rows go in opposite directions.
Discussion Questions
At 1 cm, how did turning magnet B around change what it did when released? What does that say about the stored energy?
At 8 cm, neither orientation moved. Why does turning the magnet around matter less when the magnets are far apart?
Did the north-facing-north magnet slide farther from 1 cm or from 2 cm, and how does your model explain it?
Challenge Variation
Predict, then test, what happens when magnet B is placed at 2 cm but turned sideways, so that neither pole faces magnet A. Place its bar on your model and explain the choice.
3
Fix-the-Model Card Sort
15 minPairs
Pairs get six cards. Each card shows a student's model of a two-object system: a drawing with an energy bar model and a short written description. Pairs sort the cards into "correct" and "needs a fix," then repair every card in the second pile.
The Six Cards
Card 1: Earth and a skateboarder at the top and at the bottom of a ramp. The bar is taller at the top. (Correct.)
Card 2: Earth and a framed picture hanging at 1 m and at 2 m. The description says "the energy is stored inside the picture." (Fix: the energy belongs to the Earth-picture system.)
Card 3: Two north poles 1 cm and 5 cm apart. The bar is taller at 5 cm. (Fix: like poles repel, so the 1 cm arrangement stores more.)
Card 4: A charged balloon 40 cm and 4 cm from a classmate's hair. The bar is taller at 40 cm. (Correct.)
Card 5: Earth and a basketball, first on the floor and then held 2 m up. The bar is taller at 2 m, and the description says the hand that lifted the ball added the energy. (Correct.)
Card 6: Two balloons with the same charge 30 cm and 3 cm apart. The bars are equal "because they are the same balloons." (Fix: they repel, so the 3 cm arrangement stores more.)
Discussion Questions
Three cards are correct and three need a fix. Which rule did each wrong card break?
Cards 4 and 6 both use balloons. Why does moving closer store less energy on one card and more on the other?
Pick one fixed card and add evidence: what would you see if you let go of the objects in each arrangement?
Modification for Distance Learning
Post the six cards as slides. Students mark each one correct or wrong and upload a photo of one repaired model.
03
Diagrams & Visual Aids
2 diagrams
Diagram 1: Earth and a Roller Coaster Cart at Three Positions
A model of the Earth-cart system. The cart is shown at the top of the hill (A), halfway down (B) and near the bottom (C). Each bar in the energy bar model is drawn in proportion to the cart's height above the ground in the picture, so the order is A, then B, then C. The bars show more and less, not amounts.
Diagram 2: Stored Energy of Two Magnets at Different Gaps
A model graph with no numbers on the energy axis. For like poles facing (solid line), the stored energy goes up as the gap gets smaller. For opposite poles facing (dashed line), it goes up as the gap gets bigger. Compare how far apart the two curves are at 1 cm and at 10 cm. The curves show the trend only, not measured values.
04
Homework Assignment
~30 min
MS-PS3-2 Homework: Models of Stored Energy
Directions: Every system below has two objects. Do not calculate any energy: compare more and less. Use energy bar models with no numbers, labeled drawings and full sentences. All data are invented for practice.
Part 1: Build Models (Problems 1-3)
A plant stand has three levels, 40 cm, 80 cm and 120 cm above the floor. The same flower pot can go on any level. (a) Name the two objects in the system and the interaction between them. (b) Draw an energy bar model for the pot on each level. (c) Explain what adds energy to the system when you move the pot from the 40 cm level to the 120 cm level.
Two ring magnets slide on a pencil. Rank these four arrangements from least stored energy to most: (i) opposite poles facing, 5 cm apart; (ii) opposite poles facing, 10 cm apart; (iii) like poles facing, 10 cm apart; (iv) like poles facing, 5 cm apart. Explain your ranking with the attract and repel rule.
A latex-free balloon is rubbed on a wool cloth and held 50 cm, 20 cm and 5 cm from a sheet of tissue paper strips taped to a ruler. (a) Draw a three-panel model with an arrow for the pull on the strips and an energy bar in each panel. (b) In which panel does the system store the most energy? (c) Write two sentences describing what happens to the stored energy as the balloon moves closer.
Part 2: Use Data and Critique Models (Problems 4-6)
Two toy boats float in a tub of water, each with a magnet on its side, like poles facing. They are released from different gaps, and the class measures how far apart the boats drift in total. Gap 2 cm: 30 cm. Gap 4 cm: 12 cm. Gap 6 cm: 5 cm. Gap 8 cm: 2 cm. (a) Which starting gap stored the most energy? Cite the data. (b) Draw a bar model for the four gaps. (c) Predict a range for the drift from a 3 cm gap, and explain.
A metal washer hangs on a 1 m string. It is pulled to the side and let go from 10 cm, 20 cm and 30 cm above its lowest point. After ten swings, it rises to 8 cm, 16 cm and 25 cm. (a) Which start stored the most energy in the Earth-washer system, and what is the evidence? (b) Why does the washer rise less high after ten swings than at the start? (c) Predict whether a 40 cm start would reach above or below 40 cm after ten swings, and explain with your model.
A student writes: "The energy is stored inside the magnet. A strong magnet always has more stored energy than a weak one, no matter where the other magnet is." (a) Name two problems with this model. (b) Rewrite the model in two or three sentences so it is correct for two strong magnets with like poles facing.
Rubric
Criterion
Full Credit (2 pts)
Partial Credit (1 pt)
System and Interaction
Names both objects and the interaction (gravitational, magnetic or electric) in every problem
Names the objects or the interaction, but not both
Model
Drawings and bar models show more and less stored energy in the right order for attracting and repelling pairs
Model drawn, but one ranking is reversed or the bars do not match the description
Evidence and Reasoning
Cites the data or what the objects do when released, and explains it with the rule
Gives a ranking or prediction without evidence or reasoning
Critique
Finds both errors in Problem 6 and writes a corrected model
Finds one error or rewrites the model only partly
05
Quiz: 20 Questions
Interactive, with answers
Instructions
Every system in this quiz has two objects. No question asks you to calculate energy: compare more and less. All data are invented. Your score updates as you answer, and Reset quiz clears everything so you or your students can try again.
Multiple choice: pick an option to check it. Short answer: write your answer, then reveal the model answer.
0 of 20 answered · 0 correct
Question 1 of 20 · Multiple Choice
A pinecone hangs from a branch high in a tree. For a model of its stored potential energy, which choice names the system and the interaction?
Answer: B
The pinecone and Earth pull on each other without touching, so the system is the pair, and the interaction is gravitational. Choice A treats one object as the whole system. Choice C names the branch, which touches the pinecone and holds it up but does not pull on it from a distance, and choice D names the air, which does not cause the downward pull.
Question 2 of 20 · Multiple Choice
A roller coaster cart passes four points on a track. Their heights above the ground are P: 18 m, Q: 6 m, R: 25 m and S: 12 m. At which point does the Earth-cart system store the most potential energy?
Answer: D
Earth and the cart attract, so the arrangement with the cart farthest from Earth stores the most energy: R, at 25 m. Choice A picks the first point listed, not the highest. Choice B picks the lowest point, which stores the least.
Question 3 of 20 · Multiple Choice
Two ceramic magnets have their north poles facing each other. You push them from 6 cm apart to 2 cm apart. What happens to the potential energy stored in the two-magnet system?
Answer: C
Like poles repel, so pushing them closer works against the interaction and adds energy to the system. Choice B uses the attracting-pair rule for a repelling pair. Choice A treats the energy as belonging to the magnets alone instead of to their arrangement.
Question 4 of 20 · Multiple Choice
A north pole faces a south pole, 1 cm apart. You pull the magnets to 5 cm apart. How does the stored energy change?
Answer: A
Opposite poles attract, so pulling them apart stores more energy, and your hand supplies it. Choice B applies the repelling-pair rule to an attracting pair. Choice D confuses less pull at a larger gap with no stored energy.
Question 5 of 20 · Multiple Choice
Two ring magnets on a pencil sit 1.5 cm apart with north facing north. One magnet is turned over, so north now faces south, still 1.5 cm apart. What happens to the stored energy?
Answer: C
Turning a magnet over changes the arrangement. At a small gap, the repelling arrangement stores more energy than the attracting one, so the stored energy goes down. Choice B forgets that orientation is part of the arrangement. Choice A treats a stronger pull as more stored energy, and choice D is false: an attracting pair still stores energy, which increases if you pull the magnets apart.
Question 6 of 20 · Multiple Choice
A charged balloon is moved from 15 cm to 2 cm beside a thin stream of water from a faucet, and the stream bends toward the balloon. What happens to the stored energy of the balloon-water system as the gap shrinks?
Answer: B
The stream bends toward the balloon, so the pair attracts, and for an attracting pair, moving closer lowers the stored energy; some of it goes into moving the water sideways. Choice A uses the repelling-pair rule. Choice C ignores the electric interaction, which stores energy like gravity and magnets do.
Question 7 of 20 · Multiple Choice
Two balloons are rubbed on the same wool cloth, so they carry the same kind of charge. They hang on threads. Which arrangement stores the most energy?
Answer: D
Same charges repel, so the closest arrangement, 4 cm, stores the most energy. Choice B picks the farthest arrangement, which would be right only for an attracting pair. Choices A and C are in between.
Question 8 of 20 · Multiple Choice
A book sits on a high shelf. Where is its gravitational potential energy stored?
Answer: A
Potential energy belongs to the pair of objects that interact, here Earth and the book. Choice B is the inside-one-object error. Choice C names the shelf, which holds the book but does not pull on it from a distance.
Question 9 of 20 · Multiple Choice
In a test, two magnets with like poles facing are released from three gaps. From 1.5 cm they slide apart 20 cm in total, from 3 cm 7 cm, and from 4.5 cm 3 cm. What do the data show?
Answer: D
The magnets moved farthest when released from 1.5 cm, so that arrangement stored the most energy. Choice A reverses the evidence by matching the largest gap with the most energy. Choice C ignores the differences in the data: the same magnets can store different amounts in different arrangements.
Question 10 of 20 · Multiple Choice
Which of these is a two-object system that interacts at a distance?
Answer: B
The magnet pulls the paper clip without touching it, so they interact at a distance. Choices A, C and D are contact pushes: the objects must touch to push on each other.
Question 11 of 20 · Multiple Choice
A student's energy bar model of a roller coaster shows the tallest bar when the cart is at the bottom of the hill and the shortest bar at the top. What is wrong with the model?
Answer: C
Earth and the cart attract, so the top of the hill, where they are farthest apart, stores the most. Choice A mixes up stored energy with energy of motion, which is largest at the bottom. Choice B treats the energy as fixed no matter where the cart is.
Question 12 of 20 · Multiple Choice
Two magnets are 30 cm apart. Turning one of them around makes almost no difference to the stored energy. Why?
Answer: C
The magnetic interaction gets much weaker with distance, so far apart the two orientations store almost the same energy. At 1 cm the difference is large. Choice B contradicts the official magnet example, and choice A is false: a magnet keeps its poles.
Question 13 of 20 · Multiple Choice
A chain lifts a roller coaster cart from the station to the top of the first hill. What puts energy into the Earth-cart system?
Answer: A
The chain pulls the cart up against Earth's pull, so the motor-driven chain transfers energy into the system. Choice B is the interaction inside the system, which pulls the cart down, not up. Choice D names a part of the cart that does not push it uphill.
Question 14 of 20 · Multiple Choice
Maya says, "Closer together always means more stored energy." For which system is she correct?
Answer: D
Her rule works only for repelling pairs, such as two north poles. Choices A, B and C are attracting pairs, where closer together stores less energy, not more.
Question 15 of 20 · Short Answer
A delivery drone hovers 2 m above a field, then rises and hovers 10 m above it. Describe a two-picture model of the Earth-drone system, say which picture stores more energy, and name what supplied the change.
Picture 1 shows the drone low with a short energy bar; picture 2 shows it high with a taller bar and an arrow for Earth's pull. The 10 m position stores more energy, because Earth and the drone attract and are farther apart. The drone's spinning propellers, run by its battery, pushed it up and supplied the energy.
Question 16 of 20 · Short Answer
A coaster track passes five points with these heights: J 32 m, K 8 m, L 20 m, M 27 m, N 3 m. Rank the points from most stored energy in the Earth-cart system to least, and give the rule you used.
J, M, L, K, N. Earth and the cart attract, so the higher the cart, the farther it is from Earth and the more energy the system stores. No calculation is needed: only the order of the heights.
Question 17 of 20 · Short Answer
Two magnet cars are set up with opposite poles facing. In one trial they start 6 cm apart; in another, 2 cm apart. Describe an energy bar model for the two starts, and say what you would see when the cars are released.
The 6 cm bar is taller, because opposite poles attract, so the farther-apart start stores more energy. Released from 6 cm, the cars roll together and bump harder (faster) than when released from 2 cm, because more stored energy turns into motion before they meet.
Question 18 of 20 · Short Answer
Plan a test that uses two magnet cars and a meter stick to find out which of two pairs of ring magnets, pair X or pair Y, stores more energy at a 2 cm gap with like poles facing. Name what you change, what you measure and what you keep the same.
Change only the magnet pair (X, then Y). Measure the total distance the two cars roll apart after release. Keep the same cars, the same 2 cm starting gap, the same floor and the same way of letting go, and run each pair three times. The pair whose cars roll farther stored more energy at 2 cm.
Question 19 of 20 · Short Answer
A student says, "A cat sleeping on top of a bookcase has the same energy as a cat sleeping on the floor, because neither one is moving." Write two sentences that correct the student.
Neither cat has energy of motion, but the Earth-cat system stores more potential energy when the cat is on top of the bookcase, because Earth and the cat attract and are farther apart. If the cat jumped down, it would speed up, and that motion would come from the stored energy.
Question 20 of 20 · Short Answer
An empty aluminum can lies on its side on a table. A charged balloon is held 20 cm away, and the can starts rolling toward the balloon. Describe a two-panel model (start and just before they meet) and say what happens to the stored energy of the balloon-can system.
Panel 1: can and balloon 20 cm apart, an arrow on the can toward the balloon, and a tall energy bar. Panel 2: the can close to the balloon, moving, with a short bar. The stored energy goes down as the gap shrinks, because the balloon and can attract, and that energy goes into the can's rolling motion.
0 of 20 answered · 0 correct
06
Frequently Asked Questions
10 Questions
What does MS-PS3-2 mean?
MS-PS3-2 asks middle school students to build a model showing that when two objects that interact at a distance change their arrangement, the system stores a different amount of potential energy. The code means Middle School, Physical Science, core idea 3 (Energy), performance expectation 2. The practice is developing a model, and the content is stored energy in gravitational, magnetic and electric systems.
Do students calculate potential energy in MS-PS3-2?
No. The Clarification Statement puts the emphasis on relative amounts of potential energy, not on calculations. Students say which arrangement stores more or less and back it with evidence. Formulas for potential energy come later, in high school physics (beyond this standard).
What is the assessment boundary for MS-PS3-2?
Assessment is limited to two objects and to electric, magnetic and gravitational interactions. A ball and Earth, two magnets, or a charged balloon and hair are in scope. Systems with three or more interacting objects, and stored energy in springs or rubber bands, are beyond this standard.
What counts as a model for this standard?
A drawing, a diagram, a picture or a written description of the system can all be models, as the Clarification Statement says. Strong models name the two objects, show the push or pull with arrows, compare stored energy with bars or words, and explain the comparison with evidence.
Why is the energy stored in the system and not in one object?
Because it depends on where the two objects are compared with each other. A can of soup has no stored gravitational energy by itself: the energy comes from the can and Earth pulling on each other. Saying "the Earth-can system" helps students see that changing either object's position changes the energy.
When does moving objects closer together store more energy?
Only when the objects repel, such as two north poles or two balloons with the same charge. For pairs that attract, such as Earth and a cart, opposite magnet poles, or a charged balloon and hair, moving them farther apart stores more energy. Students can check either case with what happens when the objects are released.
What mistakes do students make with MS-PS3-2?
Many students use "closer means more" for every pair, put the energy inside one object, or think a resting object stores nothing. Another frequent slip is mixing up stored energy with energy of motion. Card sorts with wrong models bring these ideas into the open.
Is the balloon and hair demonstration safe?
Yes, with simple steps. Use latex-free balloons in case someone has a latex allergy, ask a volunteer before bringing a balloon near their hair, or tape tissue paper strips to a ruler instead. Use ceramic magnets rather than small strong magnets, keep magnets away from phones and medical devices, and pick up marbles from the floor right away.
What grade is MS-PS3-2 taught in?
It is a grades 6-8 standard, and schools place it in grade 6, 7 or 8 physical science, often in an energy unit next to MS-PS3-1 on kinetic energy. It builds on grade 4 and 5 ideas about energy and gravity.
How does MS-PS3-2 connect to high school physics?
It is the base for HS-PS3-2, where students model energy as either motion of particles or energy stored in fields, and for HS-PS3-5, where they model two objects interacting through electric or magnetic fields. In high school, the same "more or less" models become calculations.
07
Related Standards
6 standards
These standards connect to MS-PS3-2: prerequisites to review first, parallel standards at the same level, and next steps that build on it.
Before this lesson
5-PS2-1Prerequisite
Support an argument that Earth's gravitational force on objects is directed down
Lesson coming soon
4-PS3-1Prerequisite
Use evidence to explain how the speed of an object relates to its energy
Lesson coming soon
Alongside
MS-PS2-3Parallel
Ask questions about data on the factors that affect electric and magnetic forces
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