Measurement of Time and Motion – Short Answer Type Questions
Class 7
Science
Chapter 8
Measurement of Time and Motion — 50 Short Answer Questions & Answers
Topic-wise short answer practice strictly aligned with NCERT for CBSE Class 7 students; ideal for revision and exam preparation.
Content Bank — Key formulas & units
- Speed = Distance / Time (s = d / t)
- Distance = Speed × Time (d = s × t)
- Time = Distance / Speed (t = d / s)
- Unit conversions: 1 min = 60 s; 1 h = 3600 s; km/h → m/s multiply by 5/18; m/s → km/h multiply by 18/5.
Time & Measuring Instruments (Q1–Q10)
1. What is the SI unit of time?
Second (s).
2. Name two instruments used to measure time.
Clock/watch and stopwatch/timer.
3. How many seconds are there in one hour?
3600 seconds (60 × 60).
4. What is a stopwatch used for?
Measuring short time intervals precisely (e.g., races, experiments).
5. Convert 2 hours into minutes.
2 hours = 120 minutes.
6. Why is it important to use the same units when calculating speed?
To ensure correct numerical results; mixing units leads to errors.
7. Give an example of a digital time-measuring device.
Digital clock or digital stopwatch.
8. What does a calendar measure?
Days, months and years — long-term time periods.
9. Define 'time interval'.
The duration between two events (end time minus start time).
10. How many minutes are there in 2.5 hours?
2.5 × 60 = 150 minutes.
Basic Concepts of Motion (Q11–Q20)
11. What is motion?
Change in position of an object with time relative to a reference point.
12. Define 'rest'.
A state when an object does not change its position with time.
13. What is distance?
Total path length travelled by an object; scalar quantity.
14. What is displacement (qualitative)?
Straight-line distance from initial to final position in a specific direction (vector concept introduced qualitatively).
15. Explain uniform motion.
Motion in which an object covers equal distances in equal intervals of time.
16. What is non-uniform motion?
Motion in which distances covered in equal time intervals are not the same.
17. Is motion of Earth around the Sun uniform? (Simple answer.)
Approximately uniform in speed; direction changes (orbital motion).
18. Give one everyday example of uniform motion.
A train moving at constant speed on a straight, level track (idealised example).
19. Give one everyday example of non-uniform motion.
A car slowing down to stop at a traffic signal.
20. Does a walking person in a circular path have constant displacement?
No — displacement changes because direction and position change.
Speed — Definitions & Formula (Q21–Q30)
21. Define speed.
Speed is the distance travelled per unit time.
22. Write the formula for speed.
Speed = Distance / Time (s = d / t).
23. If a car travels 120 km in 2 hours, what is its speed?
120/2 = 60 km/h.
24. How do you calculate distance if speed and time are known?
Distance = Speed × Time (d = s × t).
25. How do you calculate time if distance and speed are known?
Time = Distance / Speed (t = d / s).
26. What are standard units for speed?
Metre per second (m/s) and kilometre per hour (km/h).
27. A bike covers 15 km in 30 minutes. What is its speed in km/h?
30 minutes = 0.5 h; speed = 15/0.5 = 30 km/h.
28. A runner covers 100 m in 10 s. What is speed in m/s?
100/10 = 10 m/s.
29. What is average speed?
Total distance travelled divided by total time taken.
30. If a car travels 50 km in 1 h and 100 km in 2 h, what is its average speed?
Total distance 150 km; total time 3 h; average speed = 150/3 = 50 km/h.
Unit Conversions & Typical Problems (Q31–Q40)
31. How to convert km/h to m/s?
Multiply by 5/18 (m/s = km/h × 5/18).
32. Convert 36 km/h to m/s.
36 × 5/18 = 10 m/s.
33. Convert 9 m/s to km/h.
9 × 18/5 = 32.4 km/h.
34. A car travels at 20 m/s. How far will it travel in 10 s?
Distance = speed × time = 20 × 10 = 200 m.
35. A cyclist's speed is 12 km/h. How many metres does he travel in one minute?
12 km/h = 12×1000/3600 = 3.333 m/s; in 60 s: 3.333 × 60 ≈ 200 m.
36. A train travels 300 km in 4 hours. Speed = ?
300/4 = 75 km/h.
37. If speed is 5 m/s, what is time to cover 100 m?
Time = distance/speed = 100/5 = 20 s.
38. A bus covers 180 km in 3 hours. What is its speed in km/h?
180/3 = 60 km/h.
39. Why do we use conversion factors (like 5/18)?
To change units correctly because 1 km/h equals 5/18 m/s.
40. How many metres in 2.5 km?
2.5 × 1000 = 2500 metres.
Applications, Experiments & Exam Tips (Q41–Q50)
41. Suggest a simple home experiment to measure speed.
Measure a marked distance (e.g., 20 m), use a stopwatch to time walking/running, then compute speed = distance/time.
42. What is the effect of stopping (waiting) on average speed?
Stopping increases total time while distance may not change, so average speed decreases.
43. How does knowing speed help in daily life?
It helps estimate travel time and plan journeys.
44. Give two safety uses of speed knowledge on roads.
Setting speed limits; choosing safe stopping distances.
45. What should you write first when solving a speed problem?
Write down known values (distance, time or speed), convert units if necessary, then use formula.
46. A walker covers 5 km at 5 km/h. Time taken = ?
Time = distance/speed = 5/5 = 1 hour.
47. A car travels at 54 km/h. Express this in m/s.
54 × 5/18 = 15 m/s.
48. A toy car moves at 0.5 m/s. How far in 2 minutes?
2 minutes = 120 s; distance = 0.5 × 120 = 60 m.
49. If distance is zero, what is speed?
Zero (object is at rest).
50. One-line summary of this chapter?
Chapter explains how to measure time, describe motion and calculate speed using distance and time — essential basics for physics.