Schooling · Class 7 · Science · Measurement of Time and Motion · Chapter on a page
CBSE Class 7 · Science · NCERT Curiosity
Measurement of Time and Motion: chapter on a page
A cut of Shishya's notes for this chapter: the first paragraph of the introduction and the key ideas, formulas and facts, common mistakes and quick revision lists, word for word. Nothing is added or reworded; the worked examples are left out (they are on the chapter page).
About the notes: Written by Shishya's AI on 26 Sept 2026 from the chapter's title and class level, in Shishya's own words — not a copy or summary of the textbook. Read the official chapter for the book's own text, activities and exercises.
This note's current text has no applied fact-check on record.
Mind map
Drawn from the same notes by a fixed rule (no AI): each label is the item's own words — its bold term, its label before a colon, a short formula as written, or its first words.
The mind map as a list
- Key ideas
- Motion
- reference point
- Speed
- Speed = Distance ÷ Time. The common…
- Uniform motion
- Time can be measured using sundials…
- simple pendulum
- Formulas and facts
- Speed = Distance ÷ Time
- Distance = Speed × Time
- Time = Distance ÷ Speed
- 1 hour = 60 minutes = 3600 seconds
- 1 kilometre = 1000 metres
- To change km/h to m/s, multiply by…
- A longer pendulum swings slower; a…
- Watch out for
- Forgetting to use the same units for…
- Thinking that a faster pendulum has…
- Confusing rest and motion without a…
- Mixing up the formula and writing…
- Believing an object moving in a…
What this chapter is about
This chapter helps you understand two important ideas: how we measure time and how we describe the motion of objects. Time is something we use every day — to wake up for school, to catch a bus, to know when a cricket match starts. But have you ever wondered how people measured time before clocks existed?
Key ideas
- Motion means a change in the position of an object with time. If a thing stays in the same place, it is at rest.
- To know if something is moving, we compare its position to a fixed point called a reference point. A tree by the road is a good reference point.
- Speed tells us how fast an object is moving. It is the distance covered in a given time.
- Speed = Distance ÷ Time. The common unit is metres per second (m/s) or kilometres per hour (km/h).
- Uniform motion means an object covers equal distances in equal intervals of time. Non-uniform motion means distances covered are unequal.
- Time can be measured using sundials, water clocks, sand clocks, pendulums, and modern clocks or watches.
- A simple pendulum takes the same time to complete one swing if its length stays the same. This time is called the time period.
- The basic unit of time is the second (s). Larger units are minutes (60 s) and hours (60 min).
Formulas and facts to remember
- Speed = Distance ÷ Time — tells how much distance an object covers every unit of time.
- Distance = Speed × Time — use when you know speed and time but need distance.
- Time = Distance ÷ Speed — use when you know distance and speed but need time.
- 1 hour = 60 minutes = 3600 seconds.
- 1 kilometre = 1000 metres.
- To change km/h to m/s, multiply by 5/18. To change m/s to km/h, multiply by 18/5.
- A longer pendulum swings slower; a shorter pendulum swings faster.
- Ancient devices for measuring time: sundial (shadow), water clock (dripping water), sand clock (falling sand).
Common mistakes
- Forgetting to use the same units for distance and time → always convert minutes to hours (or seconds) before using the formula.
- Thinking that a faster pendulum has a longer string → actually, a shorter string makes the pendulum swing faster.
- Confusing rest and motion without a reference point → always choose a fixed reference point first.
- Mixing up the formula and writing Speed = Time ÷ Distance → remember, speed is distance divided by time, not the other way round.
- Believing an object moving in a circle is at rest because it comes back → it is still in motion because its position keeps changing.
Quick revision
- Motion is change of position with respect to a reference point.
- Speed = Distance ÷ Time; unit is m/s or km/h.
- Uniform motion: equal distances in equal times; non-uniform: unequal distances.
- A pendulum's time period depends on its length, not on its weight.
- Sundial, water clock, sand clock and pendulum clock are older ways to measure time.
- 1 hour = 3600 seconds; to convert km/h to m/s, multiply by 5/18.