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Q1. In an hourglass, time is measured on the basis of
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Q2. Candle clocks measured time by
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Q3. The hole in the bowl of the Ghatika-yantra was made such that it took approximately how long to fill and sink?
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Q4. In Activity 8.1, a Class 7 student makes a simple water clock by cutting a 1/2-litre transparent bottle, making a small hole in the cap, and placing the top inverted on the lower half. The best way for her to mark minute-intervals is to
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Q5. In Activity 8.2, students measure the time taken by a 100-cm-long pendulum to complete 10 oscillations and repeat the process 3-4 times. The main reason for repeating the measurement is to
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Q6. The pendulum clock was invented in
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Q7. The 'speed' of an object is defined as
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Q8. If distance is expressed in kilometre and time in hour, the unit of speed is
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Q9. The instrument fitted in a vehicle that measures the distance travelled by it in kilometre is called
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Q10. A Class 7 student says, 'A pendulum with a heavier bob must take more time to complete one oscillation, because heavier things are harder to move.' The teacher's best response, grounded in this chapter, is
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Q11. Prerna's sports teacher uses a special kind of watch called a stopwatch to time school races, because
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Q12. One-thousandth of a second is called
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Q13. If a bus moves at a steady speed of 40 km/h, the time it will take to cover a distance of 100 km is
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Q14. An object is in uniform motion. Distances at times 10, 20, 30, 50 and 70 s are 8, ?, 24, 40 and 56 m respectively. The missing distance at t = 20 s is
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Q15. An object covers 60 m in 100 s, with distances 0, 6, 10, 16, 21, 29, 35, 42, 45, 55, 60 m at successive 10-s intervals. The motion is non-uniform; its average speed is
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Q16. In Activity 8.3, students are asked to look at the wall clock in Fig. 8.9 and identify the smallest time interval it can measure. The activity is designed to help students directly observe that
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Q17. Activity 8.4 asks students to use a railway timetable, find a train's departure and arrival times at two adjacent stations, and the distance between them, in order to
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Q18. The 'Exploratory Projects' suggest that the pulse rate of a friend (number of pulse beats in 1 minute) can be used to
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Q19. An 'Exploratory Project' asks students to visit a playground, measure the time taken by a swing for 10 oscillations, and repeat with children of different weights and with swings of different lengths. The project ultimately tests whether the swing behaves like a
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Q20. In a 100-cm-long pendulum, the time period was measured as 2 s. Asha shortens the thread to make a much smaller pendulum. Based on the chapter's conclusion about how length affects the time period, she should predict the new time period to be
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Q21. A Class 7 student records 'one oscillation' every time the bob moves from extreme A to mean position O, instead of from A through O to B and back to A. The student's time period reading for a given pendulum will most likely be
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Q22. The 'Exploratory Projects' suggest comparing the speeds of male and female winners in 100 m, 200 m and 400 m Olympic races. To find the speed of each winner from the records, a student must
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Q23. Ravi tells his Class 7 teacher: 'A car covers 60 km in the first hour, 70 km in the second hour, and 50 km in the third hour. Its speed is therefore 60 km/h throughout the journey.' The teacher's best response, grounded in this chapter, is
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Q24. In Fig. 8.7(a), a simple pendulum is shown to consist of three parts. From top to bottom, these are
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Q25. The chapter says a pendulum also completes one oscillation when its bob moves from one extreme position A to the other extreme position B and comes back to A. The total number of times the bob crosses the mean position O during this one oscillation is
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Q26. The chapter notes that when calculating speed by total distance / total time, 'the object might not have travelled with the same speed during the entire duration of time'. The most accurate name for the speed so calculated is
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Q27. According to the 'Dive Deeper' box which pair of time-unit forms is INCORRECT in writing?
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Q28. Priya argues that uniform linear motion is 'just a textbook idea — we hardly ever see it in real life'. Based on this chapter, the best teacher response is
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Q29. Fig. 8.11 of the chapter shows a train moving along a straight track between stations A and D, with intermediate points B and C. The motion between B and C is at constant speed, while between A-B and C-D the speed changes. Which of the following is correct?
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Q30. Modern wrist watches and digital clocks marked 'quartz' keep time by using the periodic process of
