1. Shop. 80 m, steady 2 m/s. How long?
Estimate: 40 s?
Answer
80 ÷ 2 = 40 s. If you multiplied 80 × 2 you treated speed as extra metres, not metres per second.
Physics / How far / how fast
Uncut
Physics starts here · write the move
How far / how fast
A thing moves. You track how far, and how long it took. How fast is that pair. If how fast itself changes, that is a new job (sträcka, hastighet, acceleration).
— heat as a later ledger, not this page.
Origins
Always
Walks, ships, falling stones. People already compared “far” and “soon.”
Galileo
He timed a ball on a groove. Distance against time, written down. The tool is the track, not a statue of the man.
After this
Why it keeps going, what changes that, where the push’s work went. Those wait. This page is only the writing-down.
Waves sit later on this same river, after energy. This page is still where the river starts: write the move down.
Drag time. Watch how far.
Steady speed first: equal stretches in equal times. Then let speed grow, and the stretches get longer.
t = 0 s · 0 m · steady 4 m/s
Top: the mark on the road. Bottom: how far against how long. Steeper = faster. A curve up means speed itself is growing.
Sträcka mot tid. Lutning är hastighet. Om lutningen växer: acceleration.
A cut question, then a job
A car drives at 12 m/s for 5 s. Find s.
Nothing is at stake. Nobody is late.
The stop is 50 m away. You walk at about 1.5 m/s. Do you have 40 seconds, or not?
50 ÷ 1.5 ≈ 33 s. Forty seconds is enough if you keep that pace. That is a job.
Jobs — estimate first
2. Steep line. Two walks, same time. One line on the plot is steeper. Who went farther?
The steeper one.
Answer
Steeper means more metres in the same seconds — faster, farther. The flat line barely moved.
3. Speed-up. A ball starts slow and the stretches get longer each second. Is speed still one number?
No — it is changing.
Answer
One speed was the steady case. Here speed itself changes. That is the next name, after how far / how fast.
Gate — four, all required
Each right gate item is 20 points. Hands-on is 20. Wrong is 0 until you retry and get it. Next unlocks only at 100 — and only if that page exists.
1. What is this tool doing?
2. On the distance–time picture, a steeper line means…
3. 30 m at a steady 3 m/s. Time?
4. Which is a real question?