Your kids are already doing physics
Every time a car shoots off a homemade ramp, your child runs an experiment with no rules yet. A ramp is one of the simple machines (an inclined plane), and early childhood educator Ann Gadzikowski notes that kids do not need the names. They need hands-on tries1.
Using the picture book Daisy's Wild Ride, Gadzikowski explains Newton's first law: a moving object keeps going at the same speed and direction unless an unbalanced force acts on it. For young children, she says, the big idea is simpler1:
for something to stop moving, something else must get in its way.1
On a playground slide, DK's 1000 Words STEM labels two forces: gravity and friction4. A car on a ramp is the same idea. Gravity pulls it down, and friction is the something that gets in its way.
Ask a "which" question, not a "why"
"Why does my car stop?" is a lovely question and a hard one to test. Darci Harland's STEM Student Research Handbook says "why" questions are too broad and shows how to narrow them2. Her book was written for grades 9-12, so what follows is our adaptation for younger kids.
Testable questions often begin with How, What, When, Who, or Which.2
So "Why does my car go so far?" becomes "Which ramp height makes the car roll farthest?" Now your child knows exactly what to change (the height) and what to measure (the distance).
Set up a fair test
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01Ask a which question.
"Which ramp height makes the car roll farthest?" Write it at the top of a page2.
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02Pick the one thing you change.
Ramp height in tiles or books: 1, 2, 3, 4. A good spread beats just "low" and "super high"2.
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03Pick the one thing you measure.
Distance from the bottom of the ramp to where the car stops2.
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04Keep everything else the same.
Same car, same floor, same start line, let go without pushing. Scientists call these constants2.
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05Do practice runs.
Two rolls that do not count, to learn to let go cleanly. Harland calls these pretrials2.
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06Repeat and record.
Roll each height several times. Write every result down right away, even the weird ones2.
- The same car for every roll
- Let go, never push
- The same bare floor (move away from the rug)
- Measure to the same spot on the car
- Red car on the tall ramp, blue car on the short one
- A little push on one ramp, just letting go on the other
- One roll each, then announce a winner
- Half the rolls end on the rug
- The same car on every ramp height
- Let go every time, no pushing
- Three or more rolls per height
- Every roll on the same bare floor
Little kids love to help the car along. Give them the rule: "In science, the car goes by itself."
Record it and read the results
Harland is firm on two habits: write data down right away, never on scraps, and record what you saw, not an opinion like "it was good"2. Ages 5-7 can measure in hand spans or floor tiles. Ages 8-10 can use a tape measure.
| Ramp height | Roll 1 | Roll 2 | Roll 3 | Middle roll | What we saw |
|---|---|---|---|---|---|
| EXAMPLE: 2 tiles tall | 38 in | 41 in | 35 in | 38 in | Curved left once |
| 1 tile tall | ____ | ____ | ____ | ____ | ____ |
| 2 tiles tall | ____ | ____ | ____ | ____ | ____ |
| 3 tiles tall | ____ | ____ | ____ | ____ | ____ |
| 4 tiles tall | ____ | ____ | ____ | ____ | ____ |
How to read the example row: line up the three rolls from shortest to longest, 35, 38, 41. The middle one, 38, is the median2. The mean (average) is 35 + 38 + 41 = 114, divided by 3 = 38. The range is the biggest minus the smallest: 41 minus 35 = 6 inches2.
Something that can change in a test. We change one on purpose and measure another2.
Say it: “What is the one thing we are changing today?”A test where only one thing changes, so you know what caused the result.
Say it: “Did anything else change besides the ramp?”What you think will happen, said before you try it4.
Say it: “Which ramp do you think wins? Point to it.”One try of the test. More trials mean one lucky roll cannot fool you.
Say it: “Should we believe just one roll?”The rubbing that slows things down when two surfaces move against each other4.
Say it: “Will the car roll farther on the rug or on the floor?”Try it tonight
The ramp height test
- 1 toy car (the same one every time)
- Magnetic tiles, or books plus stiff cardboard
- Masking tape for the start line
- Tape measure, or paper strips for younger kids
- Pencil and the data table above
- Build a ramp 1 tile (or book) tall on a bare floor. Tape a start line at the top.
- Ask: which height will make the car roll farthest? Write the prediction down.
- Do two practice rolls that do not count. Practice letting go without pushing.
- Roll 3 times. Measure from the ramp's bottom to the back wheels. Record each roll.
- Raise the ramp to 2, 3, then 4 tiles tall. Change nothing else. Repeat.
- Compare the middle rolls. Ask: did our test agree with our prediction?
Next round, Gadzikowski suggests racing a big-wheeled toy against a small-wheeled one after kids predict which is faster1. Same ramp, same height, same start line.
Harland tells high schoolers that data that do not support a prediction are just as valuable as data that do. That holds at age six too2.
Mini activity: the marble line
This one comes from STEPS to STEM by Aaron Isabelle and Gilbert Zinn, a curriculum for upper elementary and middle school3. It shows what a moving thing does to things at rest.
Marble momentum line
- 5 or more identical marbles
- Two rulers taped down a marble-width apart, or two rows of tiles on edge
- Paper for a before and after chart
- Adult supervision: marbles are a choking hazard. Keep them away from younger siblings.
- Place 4 marbles touching in the middle of the track3.
- Gently roll 1 marble at them and watch the far end. What happens?
- Roll 2 together, then 3. Before each roll, ask: how many will roll away?
- Chart it: marbles rolled in, marbles still in the track, marbles that rolled away3.
- Challenge: roll 1 from the left and 2 from the right at the same time. Predict first.
The book also asks what happens when the marble is rolled harder. Its answer: the far marble rolls farther3. Then try a line of toy cars and treat it as a new question. Does the same pattern happen? Test it.
Myths, and what to expect by age
If the result disagrees with the prediction, the test failed.
Data that do not support a prediction are just as valuable as data that do2.
A prediction is just a guess.
Harland calls "an educated guess" misleading: a hypothesis builds on what you already know2. Ask what your child noticed last time.
Bonus for any age: let a car rolling down a ramp start a line of dominoes or blocks, a tiny chain reaction Gadzikowski suggests1. When it stalls, find the link that broke.
If you want a kit for this
Books and a piece of cardboard make a fine ramp. If you want a set built for this, our Magnetic Travel Tiles come with cars, and the tiles snap into roads and ramps the cars can drive up and down.
Build it with / Ages 5-7Magnetic Travel Tiles with CarsFlat shapes that stand up into roads and garages.$41.99GoP Toys sells the kit mentioned above. None of the sources cited tested our products.