Assam SCERT Class 7 Social Science Chapter 1 Calculation of time on earth Question Answer Solution
Assam Board Class 7 Social Science Chapter 1 Calculation of time on earth all Question’s easy Solution by expert teachers. Assam SCERT Class 7 Social Science (SST) Chapter 1 Calculation of time on earth Solution.
Board |
Assam SCERT |
Class |
7 |
Book |
Social Science (SST) |
Topic |
Question answer |
Exercises:-
1.) Answer in brief-
(a) What is the total number of the longitude on earth at 10 interval?
ANSWER:
There are 360 total number of the longitude on earth at 10 interval.
(b) What is the longitude of Indian Standard Time? (IST)
ANSWER:
82(1/2)0 is the longitude of Indian Standard Time.
(c) How many hours does the earth need to make a complete rotation of 3600?
ANSWER:
Earth requires 24 hours to make a complete rotation of 3600.
(e) What is the unit of an angular distance?
ANSWER:
The unit of an angular distance is degree (0), Minute (‘), second (“)
2.) Fill in the blanks –
(a) The circumference of the earth makes an angle of ————- at its centre.
ANSWER:
The circumference of the earth makes an angle of 66(1/2)0 at its centre.
(b) The measurement of the line of longitude is called ————-
ANSWER:
The measurement of the line of longitude is called Meridian.
(c) The angular distance of the Prime Meridian is ———– longitude
ANSWER: The angular distance of the Prime Meridian is 00longitude
(d) If a place remains away by 150E from the mid-day sun, then the time at that place will be ——- hrs.
ANSWER:
If a place remains away by 150E from the mid-day sun, then the time at that place will be 1 hrs.
3.) Say whether the following statements are true or false.
a) As a result of the diurnal motion of the earth, the western places face the sun earlier than the places in the eastern side.
ANSWER:
False.
(b) The travellers at the moment of crossing 1800 from the east have to add up a day in their time schedule.
ANSWER:
True.
(c) When it is 12 mid-night in any place on earth it indicates the end of a day and beginning of another day.
ANSWER:
False.
(d) The time difference at 1800 longitude is 12 hrs.
ANSWER:
True.
(e) A place where evening occurs lately than in Greenwich is located in west longitude.
ANSWER:
True.
4.) Choose the correct answers
(a) A traveller will have the feeling of loss/ gain in his time, if he moves to the west of Greenwich as per the GMT.
ANSWER:
A traveller will have the feeling of loss in his time, if he moves to the west of Greenwich as per the GMT.
(b) Mumbai has early sunrise than Greenwich therefore Mumbai is located at the east/west longitude.
ANSWER:
Mumbai has early sunrise than Greenwich therefore Mumbai is located at the east longitude.
(c) Time in each longitude to the east of the Prime Meridian goes ahead/back by four minutes.
ANSWER:
Time in each longitude to the east of the Prime Meridian goes ahead by four minutes.
(d) The east longitude of 83°20’/90°/82°30′ is accepted as the Indian Standard longitude.
ANSWER:
The east longitude of 82°30′ is accepted as the Indian Standard longitude.
(e) The common watch that we wear runs according to the Local time/ Greenwich Mean Time/ Indian Standard Time.
ANSWER:
The common watch that we wear runs according to the Indian Standard Time.
5.) Write down the differences between-
(a) Latitudes and Longitudes.
ANSWER:
We have to write differences between Latitudes and Longitudes.
Latitudes |
Longitudes |
1. Latitudes are the lines in parallel with equator imagined towards north and south poles. |
1. Longitudes are the lines connecting north and south poles i.e. meridians. |
2. The average distance between two consecutive parallels is approximately 111 km. |
2. Distance between two meridians at 00Latitude is 111.32 km and at 900Latitude is 0 km. |
3. Total 180 lines of Latitudes. |
3. Total 360 lines of Longitudes. |
(b) Local Time and Standard Time.
ANSWER:
We have to write differences between Local Time and Standard Time.
Local Time | Standard Time. |
1. Local Time is calculated by observing position of sun. |
1. Standard Time is calculated by taking line of longitude or meridian as standard meridian and the time in country is called standard time. |
2. Local Time causes many anomalies in the field of trade and commerce, rail and plane transportation. |
2.In India, Standard Time is calculated on the basis of local time of 82(1/2)0 meridian. |
6.) Solve the following problem –
(b) A wireless message was sent from New York (750W) city to Los Angeles (180°W) at about 12 noon. At what time was the message sent as per the local time of Los Angeles?
ANSWER:
Given that,
A wireless message was sent from New York (750W) city to Los Angeles (180°W)
Longitudinal difference between 2 places = 180°W – 750W
Longitudinal difference between 2 places = 105°W
Now,
Difference in local time = 105°W x 4
Difference in local time = 420’
Difference in local time = 420’/ 60’
Difference in local time = 7 hour.
The message sent as per the local time of Los Angeles = 7 p.m.
(c) What will be the exact time of a game to be held in Dhubri (90°E) as per its local time, when the same can be held in New Delhi (77°E) at 9 A.Μ.
ANSWER:
Given that,
Game to be held in Dhubri (90°E) as per its local time.
Same can be held in New Delhi (77°E) at 9 A.Μ.
Longitudinal difference between 2 places = 90°E – 77°E
Longitudinal difference between 2 places = 13°E
Now,
Difference in local time = 13°E x 4
Difference in local time = 52 minute.
The exact time of a game to be held in Dhubri (90°E) as per its local time = 9 A.Μ. – 52 minute
The exact time of a game to be held in Dhubri (90°E) as per its local time = 8.08 A.M