Forces and Movement
FoundationPushes and pulls make things move, speed up, slow down or stop; gravity pulls things towards the ground, so dropped objects fall.
- Force makes objects move.
- Pushes and pulls are common forces in daily life.
- Force can speed things up, slow them down or stop them.
文體小知識：說明文把知識講得清清楚楚。這一篇講推力和拉力怎樣令物件移動，還有東西為什麼永遠跌向地面。
§Text Passage
1On the first school day, Ming drags his suitcase through the gate, the monitor pushes open the classroom door, and in PE everyone pulls a rope for tug-of-war. The suitcase moves, the door opens, the rope tightens — behind them all is one common helper: force. Force is invisible and untouchable, yet it is always around us.
2Force can make things move. Pushing and pulling are the two most common forces: pushing a door, a swing or a trolley is a push; pulling open a drawer, dragging a suitcase and tug-of-war are pulls. Force can also speed things up, slow them down, or stop them completely — a goalkeeper catching a football uses force to stop it.
3Why does a ball thrown into the air always fall back down? Because the Earth is like a huge invisible hand pulling nearby objects downwards — this is gravity. A bottle let go, a falling leaf, the falling rain, even our own bodies are all held by gravity, kept firmly on the ground.
4We use force everywhere: pressing a light switch is a push, pulling up a zip is a pull, our feet press the pedals of a bicycle, and we pull a door towards ourselves to open it. When force is just right, objects behave; when we use too much, things may break and we may fall and get hurt, so ask adults to help carry heavy things.
5Be a force detective: notice when you are pushing and when you are pulling each day; on the way home, think why raindrops fall and why a paper plane finally lands. It is all gravity at work. Understanding forces and movement helps you see how the world around us works.
1Summary 重點摘要
Pushes and pulls make things move, speed up, slow down or stop; gravity pulls things towards the ground, so dropped objects fall.
2Vocabulary cards Vocabulary
A push or pull that can move things or stop them.
Force that moves something away from you, like pushing a door.
Force that brings something towards you, like pulling a suitcase.
A change of position, like a car driving forward.
To go faster and faster, like a bicycle rolling downhill.
To go slower and slower, like a bicycle climbing uphill.
To change from moving to still, like a keeper catching a ball.
The Earth's pull that draws objects towards the ground.
To drop towards the ground, like a ball let go.
The planet we live on; it produces gravity.
3Step by step Steps
- Step 1: Know that force makes things moveThe book on the desk will not walk away by itself; it moves only when you push or pull it. This shows: objects never start moving without a reason — a force is needed. Force also changes movement: making things go faster, slower, or stop completely. Try a little experiment: put a toy car on a smooth desk; a light push makes it roll slowly, a hard push makes it roll fast; push forward and it goes forward, push sideways and it turns. Both the size and the direction of a force change how things move.
- Step 2: Meet pushes in daily lifeA push is force that moves something away from you. Pushes are everywhere: opening the classroom door, pushing a swing higher and higher, wheeling a shopping trolley through the supermarket, shoving a heavy wardrobe, kicking a football away. Count them: how many pushes have you used today? When pushing, stand firm, place your palm flat on the object and use your whole body — do not poke with your fingertips, or you may slip and heavy things will not move.
- Step 3: Meet pulls in daily lifeA pull is force that brings something towards you. Opening a drawer, drawing the curtains, dragging a hand trolley, tug-of-war, pulling a kite string, tugging open a ring-pull can — all pulls. In tug-of-war the whole team pulls backwards together, the rope goes tight, and whichever side pulls harder drags the other over. Feel it: gently pull a rubber band with a friend and watch it stretch under the pull; let go and it springs back — pulls can even stretch springy things.
- Step 4: Meet gravityThrow a ball up and it always falls back; a ripe apple drops from the tree; raindrops fall from the sky. All this is the work of gravity: the Earth is like a huge invisible hand pulling nearby objects downwards. Gravity always pulls towards the centre of the Earth, which is why we call it down. Because of gravity, water flows to low places, our feet stay firmly on the ground as we walk, and whatever jumps up comes back down — nothing floats off into the sky.
- Step 5: Forces in our daily activitiesThink through a day and forces are everywhere: pulling back the quilt in the morning is a pull; pressing the light switch is a push; brushing teeth moves bristles across the teeth; unzipping the schoolbag to put in books is a pull; walking to school, our feet push backwards against the ground and the body moves forward; pushing open the flat door after school. Games too: flying a kite means pulling the line to steer it, and the slide brings us down by gravity. Knowing forces, you understand the science behind every action.
- Step 6: Use the right amount of force, stay safeThe right force does the job; too much causes trouble: a door pushed too hard bangs against the wall; a drawer yanked too fast may tumble out onto your toes; charging while dragging a heavy trolley can pitch you forward. To move heavy things properly: first judge the weight — if too heavy, ask an adult; bend your knees and lift with your legs, keeping the back straight; watch the path as you move. Be a little detective who knows both science and safety, and play happily and safely.
5Worked example Example
Example: Long must lift his heavy schoolbag onto the desk and pull a book-loaded trolley up a slope. How do pushes and pulls help him? And why does a dropped schoolbag fall to the ground instead of floating into the sky?
- Moving the bag: both hands push the schoolbag up onto the desk; it starts moving from rest — a push making things move.
- Pulling the trolley: hands grip the handle and pull towards himself; the trolley follows — a pull making things move.
- The slope needs a bigger force: pulling uphill fights against gravity, so more force is needed than on flat ground.
- The dropped bag falls: gravity pulls it downwards towards the ground, so objects never float into the sky.
- Answer: Pushing the bag and pulling the trolley are both forces making things move; going uphill needs a bigger force to fight gravity. Dropped objects fall towards the ground because gravity draws nearby objects towards the Earth — things always fall downwards.
6Common mistakes Mistakes
7Quick check Quick check
Q1Name two common forces.
Q2What can force do to objects?
Q3What force pulls objects towards the ground?
Q4What happens to a ball you let go?
Q5Is tug-of-war pushing or pulling?
8Recap Recap
- Force makes objects move.
- Pushes and pulls are common forces in daily life.
- Force can speed things up, slow them down or stop them.
- Gravity is the Earth's pull drawing objects to the ground.
- Use the right amount of force; too much causes injury.