ScienceGrade 8ages 13–14
⚽ Force changes motion
A ball rolling smoothly across a floor looks like it's "still being pushed," so a child concludes that motion always needs an ongoing force — when a force is really only needed to start, stop, or turn something, not to keep it going.
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Download on the App StoreWhat your child learns
- A force is spotted not by noise or effort, but by a change in motion.
- Starting, stopping and turning are the three changes, and a force is behind each one.
- The foot pushes only while it is touching. After that the ball carries on by itself.
- So steady motion needs no force. Only a change in it does.
The mistake most kids make here
You need a constant force to keep moving, or only engines have force.
Try one question
A force is…
Force
- a colour
- a push or pull that can change motion
- a kind of plant
Answer
a push or pull that can change motion — Yes. The definition is measured by the outcome: if the motion changed, a force acted.
How Maya teaches it
Your child tells Maya what they did in class. She teaches this topic at her desk, asks questions with tappable answers, and when the answer is wrong she explains why that answer was tempting instead of saying “try again”. She remembers what did not land and comes back to it.
Your child has it when they can: Say what a force can do to motion.
How to help at home
This mix-up comes from real experience: a bike stops pedaling and the bike stops, so it feels like force must be constantly "used up" to keep moving. What's missing from that picture is friction — the bike is still slowing because the road and air keep pushing back, not because motion itself runs out.
Tonight, spin a coin or roll a marble across a smooth table and a rough towel side by side. Ask what's different. The marble on the towel stops fast; on the table it keeps going much longer. That's the demonstration: less resistance means motion needs less force to continue, and with none at all it would never stop.
When your child says something needs "a force to keep it going," ask instead: "is anything touching it and pushing back?" If the honest answer is no — nothing is rubbing, no air is dragging — then no new force is needed for it to keep moving at the same speed.
A good sign she has it: she can look at a skater gliding on ice and say the ice needs almost no ongoing push, precisely because there's so little friction to fight.
Questions parents ask
- Why does my child think a moving object always needs a force acting on it?
- Because in everyday life, friction and air resistance are always present, so anything left alone does slow down and stop — making it look like force is required just to keep moving, when really force is only needed to change that motion.
- What's the difference between force and motion in simple terms?
- Force is a push or a pull. Motion is what's happening — speed and direction. A force changes motion (starts it, stops it, speeds it up, slows it down, or turns it); it isn't needed just to keep something going at a constant speed with nothing in the way.
- How can I show my child that no force is needed for steady motion?
- Compare a ball rolled on carpet versus on a smooth floor. The smoother surface has less friction fighting the ball, so it rolls farther on the same push — showing that less resistance, not less force, is what lets motion continue.
- How does Maya teach this differently from a textbook definition?
- Maya asks the child to spot the change in motion first — did something start, stop, speed up, slow down, or turn — and only then asks what caused it, so the child learns to find force by its effect rather than memorizing a rule.
No card needed. The first lesson is free.
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Sources: Next Generation Science Standards