Measurement of Time and Motion – Very Short Answer Type Questions
Class 7
Science
Chapter 8
Measurement of Time and Motion — 50 Very Short Answer Questions (NCERT-aligned)
Concise, topic-wise very short answers designed strictly as per NCERT syllabus for CBSE Class 7 exam standard.
Content Bank — Key formulas & units
- Speed = Distance / Time (s = d / t)
- Units: metre (m), kilometre (km), second (s), hour (h)
- Conversion: 1 min = 60 s; 1 h = 3600 s; km/h → m/s multiply by 5/18
1. What is the SI unit of time?
Second (s).
2. How many seconds are there in one minute?
60 seconds.
3. How many seconds are there in one hour?
3600 seconds.
4. Name a device used to measure short time intervals in experiments.
Stopwatch.
5. What instrument do we use to find the time of day?
Clock or watch.
6. What is a calendar used for?
Measuring long periods—days, months, years.
7. Define 'time interval'.
The duration between two events.
8. Give one example of a digital time-measuring instrument.
Digital clock or digital stopwatch.
9. What does AM and PM indicate on a clock?
AM = before noon; PM = after noon.
10. Why do we convert units when solving time problems?
To use consistent units for correct calculations.
11. What is motion?
Change in position of an object with time.
12. What do we mean by 'rest'?
An object that does not change its position with time.
13. Define 'distance'.
Total path length travelled by an object.
14. Define 'displacement' (qualitative).
Straight-line distance from start to end point with direction.
15. What is uniform motion?
Motion covering equal distances in equal times.
16. What is non-uniform motion?
Motion covering unequal distances in equal times.
17. How do we describe speed qualitatively?
As fast or slow.
18. Is speed a scalar or vector quantity?
Speed is a scalar quantity.
19. Give the formula for speed.
Speed = Distance / Time (s = d / t).
20. What are common units of speed?
m/s and km/h.
21. Convert 18 km/h to m/s.
18 × 5/18 = 5 m/s.
22. Convert 10 m/s to km/h.
10 × 18/5 = 36 km/h.
23. A car travels 150 km in 3 hours. What is its speed in km/h?
Speed = 150/3 = 50 km/h.
24. The same car covers 50 km in 1 hour. What is speed?
50 km/h.
25. If distance = 200 m and time = 25 s, what is speed (m/s)?
Speed = 200/25 = 8 m/s.
26. How far will an object go in 10 s at 3 m/s?
Distance = speed × time = 3 × 10 = 30 m.
27. A train goes 60 km in 1.5 hours. Speed = ?
60/1.5 = 40 km/h.
28. If speed = 20 m/s and time = 4 s, distance = ?
Distance = 20 × 4 = 80 m.
29. If distance = 90 km and speed = 30 km/h, time = ?
Time = distance/speed = 90/30 = 3 h.
30. A cyclist's speed is 15 km/h. How long to cover 7.5 km?
Time = 7.5/15 = 0.5 h = 30 minutes.
31. What is average speed?
Total distance divided by total time.
32. A car goes 60 km in 1 h and 90 km in 1.5 h. Total average speed = ?
Total distance 150 km; total time 2.5 h; average speed = 150/2.5 = 60 km/h.
33. Can average speed be equal to instantaneous speed?
Yes, if motion is uniform (constant speed).
34. Convert 36 km/h to m/s.
36 × 5/18 = 10 m/s.
35. Convert 9 m/s to km/h.
9 × 18/5 = 32.4 km/h.
36. Name one activity where a stopwatch is useful.
Timing a race or experiment.
37. If an object returns to its starting point, what is its displacement?
Zero (qualitatively).
38. Why do we use m/s in scientific calculations?
Because metres and seconds are SI units, making calculations consistent.
39. What does a speedometer in a car measure?
Instantaneous speed of the car.
40. Name two units of distance.
Metre (m) and kilometre (km).
41. A bus stops at a station for 5 minutes. Does this affect average speed? (Yes/No)
Yes — it increases total time, reducing average speed.
42. What happens to speed if distance doubles but time remains same?
Speed doubles.
43. How many metres are there in 2 km?
2000 metres.
44. How many minutes are there in 2.5 hours?
2.5 × 60 = 150 minutes.
45. What is the speed of an object that covers 0 m in 10 s?
Speed = 0 m/s (object is at rest).
46. A walker takes 2 h to cover 10 km. What is his speed in km/h?
10/2 = 5 km/h.
47. If a car travels at 72 km/h, what is its speed in m/s?
72 × 5/18 = 20 m/s.
48. A toy car moves at 0.2 m/s. How far in 1 minute?
Distance = 0.2 × 60 = 12 m.
49. A runner increases speed from 5 m/s to 10 m/s. How does this affect time to cover fixed distance?
Time reduces to half for same distance.
50. State one practical use of knowing speed in daily life.
Estimating travel time for journeys (e.g., planning arrival time).
