Things That Move
FoundationA changed position means motion; positions are relative, and speed needs comparing.
- An object whose position changes is in motion.
- Front, back, left, right, near and far are relative — say what you compare with.
- Swings, buses and footballs all show changed positions.
文體小知識：探究記敘帶你觀察生活中的運動情景，一邊比較一邊找出判斷快慢的方法。
§Text Passage
1Our world is moving everywhere: birds fly, fish swim, buses run along the roads and pupils dash about the playground. To tell whether something is moving, look whether its position changes: when an object moves from one place to another, it is in motion.
2Position is relative: to say something is in front or behind, left or right, we must say compared with whom. In a queue I stand in front of Ming but behind Lin; the window is on my left but on the teacher's right. Near and far are relative too: the playground is near the classroom, the airport is far from the city.
3After an object moves, its position changes. On a swing, the seat swings to and fro, now in front and now behind. Taking the bus to school, we move with the bus from home to school. In a football match, the ball is kicked and rolls to another place. A changed position is the proof of motion.
4Motion can be fast or slow. To compare speed, take the same distance and see who uses less time, or take the same time and see who goes farther. After school the bus takes ten minutes home but walking takes thirty, so the bus is faster. In a sprint, the one who crosses the line first is the fastest.
5Knowing how to watch motion, we can describe the world: windmills turning, raindrops falling, lifts going up and ships sailing. Play safely: hold the swing ropes tightly with both hands and look around before chasing games. Be a careful little observer — the science of motion is great fun!
1Summary 重點摘要
A changed position means motion; positions are relative, and speed needs comparing.
2Vocabulary cards Vocabulary
The change of position of an object.
The place where an object is.
Direction words for position; they depend on what we compare with.
Direction words for position; they may differ from person to person.
Words to describe distance.
Playground equipment that swings to and fro.
A common public vehicle in Hong Kong; it travels fast.
Words to describe the speed of motion.
To see which is faster or which is farther.
A ball game played with the feet; the ball moves when kicked.
3Step by step Steps
- Step 1: Know what motion isAn object is in motion when its position changes. A bird flies from a branch to a wire — its position changes, so it moves; a tree stays in one place — it does not. First choose a reference: taking the classroom as the standard, a pupil in the corridor changes position and is moving, while a desk stays still. With this method we can judge what moves and what is still around us.
- Step 2: Position is relativeWe describe position with front and back, left and right, near and far — all relative. In a queue, the pupil in front of me may be in the back row for the teacher; turn around and left and right swap sides. So always say what you compare with: I am in front of Ming; the playground is farther than the hall. Play a position game with friends — one says a direction, the other follows — and you will feel how relative position is.
- Step 3: Motion changes positionBefore and after moving, an object is in different places — the direct proof of motion. On a swing the seat swings to and fro, its position changing all the time; on the bus we travel from home to school; in football the ball is kicked towards the goal and changes place at once; on the slide we glide from the top to the ground. Up, down, front or back — a changed position means motion.
- Step 4: Compare fast and slowSpeed can be compared: over the same distance, less time means faster; in the same time, more distance means faster. After school the bus reaches home in ten minutes but walking takes thirty — the bus is much faster. At recess the fast runners reach the other end of the playground first. Watch around: planes are faster than buses, trams faster than walkers. For a fair comparison, remember two rules: same distance, compare time; same time, compare distance.
- Step 5: Scenes of motion in lifeMotion is everywhere: lifts carry us up and down, ships sail slowly along Victoria Harbour, escalators take us out of the station, and wind sways the leaves. In the park the swing swings to and fro, children glide down the slide, and bicycle wheels spin on and on. Describing these scenes with front and back, near and far, fast and slow, we observe the world more and more carefully.
- Step 6: Be safe while movingSafety comes first in play and motion: on the swing hold the ropes with both hands, swing gently and never stand on the seat; before chasing in the playground, check for other children; on the bus sit still or hold the handrail, because the body sways when the bus turns; cross the road on the green light and watch the speed and distance of the cars. With safety in mind and science in our eyes, play is both happy and safe.
5Worked example Example
Example: After school, Jun walks home from school in thirty minutes; his elder sister takes the bus along the same road and gets home in ten minutes. Who moves faster, and how do you know?
- Look at the conditions first: they travel the same road, from school to home, so the distance is the same.
- Then compare the time: walking takes thirty minutes, the bus takes ten.
- Over the same distance, less time means faster — the sister on the bus is faster.
- Think of it the other way: in the same time the bus travels farther, so it is faster too.
- Answer: Over the same distance, the one who uses less time moves faster. The sister takes ten minutes by bus and Jun takes thirty on foot, so the sister is faster. That is how we compare speed: same distance, compare time; same time, compare distance.
6Common mistakes Mistakes
7Quick check Quick check
Q1How do we know an object is in motion?
Q2What must we note when describing position?
Q3How does a swing move?
Q4What is a fair way to compare speed?
Q5What should we do on a bus?
8Recap Recap
- An object whose position changes is in motion.
- Front, back, left, right, near and far are relative — say what you compare with.
- Swings, buses and footballs all show changed positions.
- Over the same distance, less time means faster motion.
- Play safely: hold the handrail and look around.