CBSE Class 7 · Science
Measurement of Time and Motion
Official NCERT chapter from Curiosity (book code gecu1). ExamMaster notes are original teaching at CBSE Class 7 depth.
This lesson follows the official chapter “Measurement of Time and Motion” in Curiosity. The words below are ExamMaster’s teaching, not a paste from the book. Use the NCERT chapter for the classroom sequence; use these notes to hold the idea without copying exercises or figures.
- CBSE Class 7
- Easy level
- 8 concepts
1Measurement of Time
Time is measured with a repeating event you trust: a clock’s tick, a simple pendulum as taught, a Sun-shadow if that was the lesson. A number without a unit (second, minute) is mute.
“A while” is not a measurement.
Figure. Time is measured by a repeating event. A simple pendulum at one side of rest has length L; one to-and-fro is the period T. Count swings; do not draw the missing arc.
How it works
- Pick a repeating event or a clockThe tool.
- Count the repeats, or read the clockThe number.
- Write the units, min, h.
2Slow or Fast
Slow or fast compares two motions against the same time, or two times against the same stretch. Fast is more stretch in the same time, or the same stretch in less time.
A bigger vehicle is not automatically faster.
Figure. Same 100 m path. Slow or fast is the time taken: 8 s is faster than 20 s. The longer bar is the slower trip, not the longer road.
How it works
- Name the stretch or the time you will keep fairThe compare.
- See which motion covers more stretch per time (or less time per stretch)Faster.
- Write both measurementsNot a shrug.
3Speed
Speed is stretch divided by time: km/h, m/s. It is a rate, not a stretch alone and not a time alone. 30 km in 2 h is 15 km/h.
30 km is not a speed; 2 h is not a speed.
Figure. Speed is distance over time. One hundred metres in 10 s is 10 m/s. Name both measured numbers before you write the quotient.
How it works
- Measure the stretchkm or m.
- Measure the timeh or s.
- Divide stretch by time and keep the unit pairThe speed.
15 km/h
A bus covers 30 km in 2 hours. What is its average speed?
- Stretch30 km
- Time2 h
- Speed15 km/h
Pro tip. Speed is the pair: kilometres per hour, not 30 alone.
4Uniform and Non-uniform Linear Motion
Uniform linear motion covers equal stretches in equal times along a straight path. Non-uniform does not — the speed changes. A straight road does not force uniform; you still check equal stretches in equal times.
A curved path can wait; this heading is linear — along a line.
Figure. Uniform linear motion is a straight distance–time graph through the origin. Non-uniform motion bends: equal time slices add unequal distance.
How it works
- Pick equal time-slicesThe fair cuts.
- See if the stretches matchUniform if they do.
- If a slice is longer or shorter, call it non-uniformThe sort.
5A definition is a test you can run
A second is a test: a unit on a clock you can read. If you cannot say what you counted, you do not yet have a time-measurement.
A phone animation is not a second unless you read its clock.
Figure. A definition of speed is a test you can run: measure a distance and a time, then divide. Saying it looks fast is not that test.
How it works
- Read a clock or count a taught tickThe object.
- Write number plus unitThe test.
- Mute numbers get refusedThe definition ran.
6Name the given before the unknown
The given are stretch and time (or two motions). The unknown is speed or which is faster. Write both givens before you divide.
Dividing time by stretch because the larger number “should be on top” is a silent swap.
Figure. Name the given distance and time before the unknown speed. Here 100 m in 10 s gives v = 10 m/s.
How it works
- Copy stretch and timeThe given.
- Name speed or the compareThe unknown.
- Then divide or compareGiven first.
7One worked case is enough at this class
One speed is enough. A page of 30 km in 2 h clones does not add a new rate.
Ten twins of 15 km/h are still one idea.
Figure. One worked speed is enough: 200 m in 25 s is 8 m/s. Extra vehicles with the same quotient do not add a new idea.
How it works
- Compute one speedThe case.
- A second only as a checkOptional.
- StopThis class.
8A miss: swapping the school name for the picture
A race photo is a setting. The science is stretch-over-time. Crowning a winner from the photo without times is the swap-miss.
A blurred picture is not 15 km/h.
Figure. A miss is swapping the school book name for the picture. Speed lives in a measured path and a measured time, not in the chapter title.
How it works
- Keep the race as a storyA setting.
- Write stretch and timeThe science.
- Then speed or fasterDo not swap.
30 km in 2 h is a speed of
- 15 km/h
- 30 km/h
- 2 km/h
Stretch divided by time.
Notes
- Mapped to the official NCERT chapter “Measurement of Time and Motion”. Original teaching only — no textbook sentences.
- Science here is Physics, Chemistry and Biology ideas at this class, never a language or social-science chapter.
Formulas
- speed = distance / time
- unit pair: m/s or km/h
Recap
Hold these pegs from the official chapter “Measurement of Time and Motion”. The wording is ExamMaster’s teaching, not a textbook recap.
- Measurement of Time
- Time is measured with a repeating event you trust: a clock’s tick, a simple pendulum as taught, a Sun-shadow if that was the lesson.
- Slow or Fast
- Slow or fast compares two motions against the same time, or two times against the same stretch.
- Speed
- Speed is stretch divided by time: km/h, m/s.
- Uniform and Non-uniform Linear Motion
- Uniform linear motion covers equal stretches in equal times along a straight path.
- A definition is a test you can run
- A second is a test: a unit on a clock you can read.
- Name the given before the unknown
- The given are stretch and time (or two motions).
Practise Measurement of Time and Motion
Reading is free and needs no account. Practice, mocks and progress live in the app.
- A 4-question practice set that ends the chapter
- 1 quick check with worked explanations
- Timed mocks scored with the real marking scheme
- Readiness tracked per topic, kept on your device