Chapter-13
Motion and Time
Sr NO. | QUESTION | ANSWER |
21. | The metallic ball of the pendulum is called the ____ of the pendulum. | Bob. |
22. | Give an example of a periodic or oscillatory motion | When the bob of the pendulum is released after taking it slightly to one side, it begins to move to and fro. The to and fro motion of a simple pendulum is an example of a periodic or an oscillatory motion. |
23. | When we can conclude that pendulum completed one oscillation? | The pendulum is said to have completed one oscillation when its bob, starting from its mean position O, moves to A, to B and back to O. The 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. |
24. | What you mean by time period of a pendulum? | The time taken by the pendulum to complete one oscillation is called its time period. |
25. | The time measured by _____ clocks is much more accurate than that by the clocks available earlier. | Quartz. |
26. | The basic unit of time is a_____. | Second. |
27. | The basic unit of time is a Second. Its symbol is ___. | s (small english alphabet letter 's') |
28. | Larger units of time are _______ and_______. | Minutes (min), hours (h). |
29. | What would be the basic unit of speed? | Since the speed is distance/time, the basic unit of speed is m/s. Of course, it could also be expressed in other units such as m/min or km/h. You must remember that the symbols of all units are written in singular. For example, we write 50 km and not 50 kms, or 8 cm and not 8 cms. |
30. | How many seconds there are in a day and how many seconds in a year. Can you help him? |
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31. | How many hours in a year? |
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32. | The pulse of a normal healthy adult at rest beats about 72 times in a minute that is about ____ times in 10 seconds. | 12 (approximately). |
33. | How time was measured when pendulum clocks were not available. | Sundials, water clocks and sand clocks were used before the discovery of pendulum. |
34. | Rocket launching satellites into earth's orbit, often attain speeds up to _____ /s. 8 km. | 8 km. |
35. | A tortoise can move only with a speed of about ____/s. | 8cm. |
36. | How fast is the rocket compared with the tortoise? |
Speed of a rocket is 8 km/s.
Speed of a tortoise is 8cm/s
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37. | How can find the distance covered by an object in given time. | By multiplying speed by time we can calculate distance covered by an object in given time. Distance covered=Speed X Time. |
38. | How can find the speed taken by an object in a given time. | Find the time an object would take to cover a distance while moving with a given speed. Timetaken = speed/distance |
40. | What is the device to calculate the distance covered by a vehicle. | Odometer. |