Gravity Racer Lab

Explore a ramp race with your child

Help your child make a fair comparison between two car designs on the same ramp.

🏁

Start with the car in front of you. Move one control and watch the car change.There are no hidden speed points: the sliders change the model.

LIVE BUILDBalanced starter

Nallo’s guide for parents

Before the first test

The setup is ready. Ask your child what they expect, then start the test.

Steps

Ask your child: “Which car do you expect to need less time on this ramp?”
Start the prepared test after discussing your predictions.
Compare finish times together: a smaller time means a faster trip.

Your gravity racer0.8 m drop · 4.0 m track

BODY0.45 kg

WHEELS4.0 cm

SHAPENormal

TRACK0.8 m

Change one part. The car should visibly change before you race.Physics model · no hidden bonuses

Make a guess

How fast will it finish?

2.2 s

fastslow

Discuss the observation

Ask your child what changed and what stayed the same.

READYCan you beat 1.8 seconds?

Change one thing, predict, then race. That makes cause and effect easier to see.

Show the numbers

Finish time—your guess: 2.2 s

Finish speed—at the finish

Stored energy—m · g · h

Biggest loss——

WHAT TO TRYRace the starter first.

Then change exactly one visible part and race again.

A closer look at this test

💡What your race teaches

Gravity supplies the energy. Wheels, axles and air resistance decide how much of it becomes useful speed.

Race once, then change exactly one visible part.

Where does the speed go?

The ramp gives the car energy. Some makes the wheels spin; some is lost to the air, the tires and the axles.

Try it: change only the body shape and race again. Watch whether air becomes the biggest loss.

An explanation to share

How you can explain it

Gravity pulls the car down the ramp. The wheels must turn too. Rubbing at the wheels and axles, and pushing through the air, slow the car down.

FrictionRubbing that slows moving things down.

Away from the screen

An activity for you to guide

Make a small ramp from a book and a piece of stiff cardboard.
Roll the same toy car from two different start heights. Do not push it.
Keep the finish line in the same place and compare the trips.

Explanation guide for parents

Stay with your child throughout the experiment. Read the task together, compare your predictions and start the test. Operate the controls, then discuss what changed.

Support your child’s reasoning

Make sure children compare times in the right direction: less time means faster. Ask them to keep the ramp fixed when testing changes to the car.

Ask: “What did you change? What did you notice? What will you try next?” A different result is a clue, not a bad score.

Screen and real life

Real handmade cars may wobble or rub against the track. This straight ramp gives you a simpler place to compare changes.

Use the simulation to discuss patterns. You remain responsible for choosing and supervising any physical activity; real results can differ.

A question to take it further

What should stay the same if we want to test only the body shape?

A common misunderstanding

Larger wheels are not a universal guarantee of speed. Wheel rotation, axle losses and air resistance interact; the comparison applies to these settings.

How the model works

Rigid 4 m straight incline; four solid-disk wheels; no wheel slip; simplified rolling loss, axle-friction torque and quadratic air drag. The relationships are physics-based, while real handmade cars add alignment, wobble and surface effects.

Quick guide: s = seconds · m = metres · cm = centimetres · g = grams · kg = kilograms.

BUILD 20 · PARENT GUIDE · 29 SEP 2026