This unit investigates gravity, force, motion, and friction, then applies those ideas to a machine that helps a user. LEGO may be used for wheels, axles, or frames, but cardboard and household materials remain equally valid.
Use Unit 3 Student Pages.
Time: 65 minutes Big question: How can a design change the way an object falls?
The student will:
- describe gravity as a force pulling objects toward Earth;
- compare falling designs;
- measure fall time with repeated trials;
- revise a design to increase air resistance or stability.
Prepare a safe drop location approximately two meters high, such as beside a stair landing with the student remaining on the floor while the adult drops. Gather coffee filters, printer paper, string, tape, paper clips, and a timer.
Print Student Page 9.
The adult performs drops from any elevated position. Do not stand on chairs or railings. Keep the landing area clear and use only lightweight objects.
Refer to Psalm 19:1 and say:
Familiar things can still fill us with wonder. Gravity acts so consistently that we may stop noticing it. Today we will slow down and study its effects.
Gravity pulls objects toward Earth. Air resistance acts against falling motion. A broad, stable parachute shape can increase drag and slow a lightweight load. Results will vary because short fall times are difficult to time precisely.
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Drop a flat sheet and a tightly crumpled sheet from the same height.
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Ask:
They contain the same amount of paper. Why might their motion differ?
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Repeat, releasing them as simultaneously as possible.
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Build a small parachute from a coffee filter or square of paper, four equal strings, and one paper-clip load.
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Predict the fall time.
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Conduct three trials from the same height.
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Change one feature: canopy size, canopy shape, string length, or load.
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Conduct three more trials.
The crumpled paper usually lands before the flat sheet because it experiences less air resistance relative to its weight. A well-opened parachute should slow the paper-clip load.
Avoid saying gravity is weaker on the parachute. Say:
Gravity still pulls downward. The broad canopy creates more air resistance opposing the fall.
Use slow-motion video, increase the safe drop height, or compare which lands first rather than insisting on precise seconds.
Complete Student Page 9.
Design a parachute that lands a two-paper-clip load slowly and upright. State the tradeoff between load and fall time.
Time: 70 minutes Big question: How does the starting position of an object affect its motion?
The student will:
- connect ramp height with changes in motion;
- use repeated trials and consistent measurement;
- compare distance and time as different measurements;
- improve the ramp investigation from Unit 1.
Reuse the ramp from Lesson 3. Gather a toy car, books, tape, measuring tape, timer, and optional phone slow-motion camera.
Print Student Page 10.
Clear the path and keep fingers away from wheels during release.
Say:
Dependable patterns allow people to design safely. Careful testing is one way we love our neighbors when a design affects them.
Raising the starting position gives the car more stored energy related to position. As the car descends, that energy contributes to motion. This lesson does not require formal vocabulary such as kinetic or potential energy, though an interested student may learn it.
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Review the Lesson 3 data.
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Ask:
What would make our earlier test more reliable or precise?
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Let the student improve the release system, ramp stability, or measurement marks.
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Choose low and high starting positions.
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Conduct five distance trials at each position.
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Mark every stopping point with small pieces of tape.
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Discuss the spread of results.
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Optional: time travel over a fixed one-meter distance. Explain that measuring speed fairly is harder than it first appears.
The higher starting position should generally produce more motion and greater travel distance. Trial values will form clusters rather than matching exactly.
Formal averaging is optional. Say:
We can look for the center of the cluster or choose the middle value after ordering the results. That helps us compare typical performance.
Inspect whether:
- the car leaves the ramp roughly;
- the ramp bends;
- wheels rub against the ramp edge;
- the car flips or bounces;
- release points differ.
Record the observed mechanism. An unexpected result may reveal a design limit.
Complete Student Page 10.
Create a target zone and design a release height that makes the car stop inside it in three of five trials. This is an engineering-control problem, not a maximum-distance contest.
Time: 65 minutes Big question: When is friction helpful, and when does it resist motion?
The student will:
- compare motion across different surfaces;
- describe friction as a force resisting motion between surfaces;
- recognize that friction can help or hinder;
- choose a surface for a specific design need.
Gather the ramp and car plus four test surfaces, such as smooth cardboard, towel, wax paper, and a rubber shelf liner. Tape each surface flat over the same test area.
Print Student Page 11.
Avoid loose surfaces that could cause a person to slip. Conduct the test on the floor and remove materials immediately afterward.
Say:
A property can be useful in one situation and difficult in another. Wisdom means asking what a design is for before deciding what is best.
Friction opposes relative motion between contacting surfaces. Greater friction may shorten the car's travel but can provide grip. Shoes, tires, brakes, and hands all depend on useful friction.
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Rub hands gently together and notice warmth from friction.
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Ask:
Is friction always a problem?
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Choose one ramp height and release point.
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Predict which surface will allow the greatest distance.
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Conduct three trials per surface.
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Record distance and qualitative observations such as wobble or wheel slip.
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Rank surfaces from least to most resistance in this setup.
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Present design scenarios:
- a playground slide;
- a shoe sole;
- a car brake;
- a moving box.
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Have the student choose useful surface properties for each.
The car will generally travel farther on smooth, hard surfaces and stop sooner on rough or soft surfaces. Softness may also absorb energy or interfere with wheels, so the test involves more than surface roughness alone.
Our test shows how this car behaved on these materials. It does not prove one material always has "more friction" in every situation.
Complete Student Page 11.
Make a controlled stopping system that keeps the car inside a 20-centimeter zone. The student may use surface choice, a barrier, or a gentle incline.
Time: 75 minutes Big question: How can parts work together to make a task easier?
The student will:
- observe a real user need;
- use one or more mechanisms;
- define criteria and constraints;
- test and revise a working model.
Two days before the lesson, ask the student to notice small, safe household tasks that could be easier. Approve a problem before lab day.
Possible problems:
- moving pencils from one container to another;
- retrieving a lightweight object from under furniture;
- raising a small flag or sign;
- transporting toy supplies across a table;
- dispensing one index card at a time;
- keeping a book open without damaging it.
Gather cardboard, string, craft sticks, straws, rubber bands, tape, cups, bottle caps, and optional LEGO wheels, axles, gears, or frame pieces.
Print Student Page 12 and the Engineering Design Page.
Build a model. Do not design medical devices, climbing equipment, restraints, weapons, pet devices, or anything that bears a person's weight.
Refer to Mark 12:31 and Philippians 2:4. Say:
Good design begins by paying attention to another person's real need. A machine does not need to be complicated to be an act of service.
Simple mechanisms can change force or motion:
- a wheel and axle helps rolling;
- a lever pivots around a support;
- a pulley changes the direction of a pull;
- an inclined plane spreads lifting over a longer distance;
- gears transfer and alter rotation.
The child does not need to use every mechanism.
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Interview the intended user.
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Complete:
The user needs a way to __________ because __________.
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Write two measurable criteria and two constraints.
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Sketch three ideas. Require labels and arrows showing motion.
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Choose one idea based on the criteria.
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Build a mechanism test before making the full device.
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Assemble Prototype 1.
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Let the user test it if safe.
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Record where the device succeeds and where it fails.
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Make one evidence-based revision and retest.
- "Show me where force enters the system."
- "Which part moves next?"
- "Where is energy being lost to bending, rubbing, or slipping?"
- "Does the device solve the user's problem, or only perform an interesting motion?"
- "What is the smallest change worth testing?"
Say:
LEGO may be one material. First draw the mechanism without choosing a material. Then decide which parts need bricks and which might work better with cardboard, string, or another material.
Say:
Decoration can come after the function passes its tests. Which criterion have we demonstrated so far?
Complete Student Page 12 and the Engineering Design Page.
Ask the student to trace force and motion through the machine and identify where gravity or friction helps or hinders it.
Complete Progress Notes.
Add the circuit from Unit 2 as a signal, motor, or indicator only if it genuinely improves the user's experience. Test the mechanical and electrical systems separately before combining them.