Maharashtra Board Class 7 Geography Solution Chapter 3 – Tides
Balbharati Maharashtra Board Class 7 Geography Solution Chapter 3: Tides. Marathi or English Medium Students of Class 7 get here Tides full Exercise Solution.
|Maharashtra Class 7|
(Q1) Prepare a chain by matching the following.
|Group – A||Group – B||Group – C|
|Waves||8th phase of the moon (Quarter)||Objects get thrown towards the outer side|
|Centrifugal Force||New moon day||Highest high tide occurs on this day|
|Gravitational Force||Rotation of the earth||These are also generated due to earthquake and volcanoes
|Spring Tide||The moon, the sun and the earth||The force of the sun and the moon operate in different directions|
|Neap Tide||Wind||Operator in the direction towards the center of the earth|
|Group – A||Group – B||Group – C|
|Waves||Wind||These are also generated due to earthquake and volcanoes
|Centrifugal Force||Rotation of the earth||Objects get thrown towards the outer side|
|Gravitational Force||The moon, the sun and the earth||Operator in the direction towards the center of the earth|
|Spring Tide||New moon day||Highest high tide occurs on this day|
|Neap Tide||8th phase of the moon (Quarter)||The force of the sun and the moon operate in different directions|
(Q2) Give geographical reasons.
(1) Tides are influenced more by the moon than the sun.
Ans: – Tides are influenced more by the moon than the sun because the moon is closer the earth than the sun.
(2) At some places along the coast, the low lying areas turn into lagoons or marshy land.
Ans: – The sea water moves up and down or slightly forward and backward due to the waves. The waves bring the energy contained in them to the coast and they break in the shallow waters near the coast. Hence, at some places along the coast, the lying areas. Turn into lagoons or marshy land.
(3) Place located on the opposite meridian to the place experiencing high or low tide will also experience high or low tide respectively.
Ans: – Due to the centrifugal force place located on the opposite meridian to the place experiencing high or low tide will also experience high or low tide respectively.
(Q3) Answer in brief.
(1) If there is high tide at 7am, find the timings of the next high and low tides in the same day at a given place.
Ans: – If there is a high tide at 7am, then the timings of the next high tide will be at 7:25 pm as high tides occur 12 hours and 25 minutes apart. It also takes 6hours and 12.5 minutes to go from high to low tide. That means the low tide will be occurred at 1: 12.5 pm.
(2) If at Mumbai (73° E meridian), there is high tide at 1.00 pm on Thursday, then on which other meridian will there be high tide too? State with reasons.
If at Mumbai(73oE meridian), there is a high tide at 1:00 pm on Thursday, then on 253o W meridian too, there will be high tide at same day and same time. As we know a place on the earth located at the opposite point of the place experiencing high or low tide also experience high or low tide respectively at the same time. And 253o w meridian is exactly opposite to the 73o E meridian.
(3) Explain the reasons for the generation of waves.
Ans: – Generation of waves is a natural and regularly accruing phenomenon. The sea water gets pushed by the wind and ripples are generated on the water surface. These are called waves. The main reasons of wave generation is wind, but at times, due to earthquakes or volcanic eruptions occurring below the floor of the sea, waves get generated.
(Q4) In what way will the following depend on the tides?
(2) Steering a ship
(4) Salt pans
(5) Going to coastal areas for trips.
Ans: – A lack of an understanding of the timings of high and low tides may cause accidents to swimmers entering the sea.
(2) Steering a ship:
Ans: – Ships can move up to the ports during high tide
Ans: – With the high tide, fish move into the creeks and this helps fishing activity.
(4) Salt pans:
Ans: – During high tide, sea water can be stored in salt pans from which salt can be obtained.
(5) Going to coastal areas for trips:
Ans: – While going to the coastal areas for trips we must take adequate care regarding the timing of the tides otherwise it can lead to serious accidents.
(Q5) Observe big 3.8 of neap tide and answers the following questions.
(1) Which phase of the moon does it show?
Ans: – It shows the first and the third quarter phase of the moon.
(2) What are the relative positions of the moon, the sun and the earth?
Ans: – In this big. The moon makes a right angle with respect to the earth and the sun.
(3) What effect will it have on the tides?
Ans: – Due to neap tide, the water level rise is a little lower than the average high tides and a little higher than the average low tides.
(Q6) Differentiate between
(1) High tide and low tide:
Ans: – The most obvious difference between low tide and high tide is the water level on the tidal range at a given point. During high tide, the tidal range is dramatically large and on the other hand during low tide the tidal range is small.
A place on the earth located at the opposite point of the place experiencing high or low tide also experiences high or low tide respectively at the same time. When there is high tide at 0o meridian, the 180o meridian also experiences high tide. On the other hand, the meridians that are at right angles to those having high tide will experiences low tide at the same time.
After reaching the maximum water level during high tide, the low tide sets in. On the other side, after reaching the lowest water level during the low tide, the high tide sets in.
(2) Spring tide and neap tides.
Ans: – Spring tide occurs on new moon day and full moon day. Neap tide occurs on the first and the third quarter of each month.
Spring tide occurs due to the gravitational pull of the sun and the moon act in the same direction. On the other hand, neap tide occurs due to the forces of both the sun and the moon operates at right angles on the earth.
The water level during spring tide is higher than the average high tides and lower than the average low. On the opposite, the water level during neap tide is a little lower than the average high tides and a little higher than the average low tides.
(Q7) Describe the positive and negative effects of tides.
Ans: – The positive effects of tides are –
With the high tide fish move into the creeks and this helps fishing activity.
The tides clear the waste and hence the coasts become clean
Ports do not get filled with sediments
Ships can move up to the parts during high tide
During high tide, sea water can be stored in salt pans from which salt can be obtained
The tidal force can be used to generate electricity.
The tides help in maintaining the mangroves and the coastal biodiversity.
The negative effects of tides –
A lack of an understanding of the timings of high and low tides may cause serious accidents to the swimmers, fishers and visitors entering the sea.
Extra Questions and Answers Notes
1 .) What is tides ?
A:- Under the influence of the gravitational force outside the earth,
the waters of the earths oceans and rivers swell and it is called tide.
2.) After ___________ hours and __________ minutes, a cycle of high tide and low tide is completed.
A:- 12 hours and 25 minutes
3.) What is centrifugal force ?
A:- A centrifugal force is an external imaginary force experienced by an object moving in a circular motion away from the centre of rotation.
4.) How many types of tides are there and what are they?
A:- We usually see two types of tide – spring tide, and neap tide.
5.) What is spring tide ?
A:- On the day of the new moon and full moon the gravitational pull of the sun and the moon are on the same side. This causes the tidal water to rise much higher than on other days which is called spring tide.
6.) What is neap tide ?
A:- As it orbits the earth it forms a right angle with the moon sun and earth. This is due to the equivalent gravitational effect of the moon and the sun the tide that is created compared to the high tide and the low tide is called neap tide.
7.) What is tidal range ?
A:- The difference between the water level of the high tide and low tide is called tidal range.
8.) The amount of tidal range in the open sea is about ______________________ .
A:- 30 cm
9.) Where on the earth is the highest tidal range seen and what is its extent ?
A:- The bay of fundy is the highest tidal range on the north American atlantic coast, its extent about 1600 cm.
10.) The highest tidal range in india is in ____________________ .
A:- Gulf of Khambhat
11.) Write five good effects of the tide.
A:- The effects of the tide are –
1.) As a result of the tide the fish move into the creeks which helps the fishermen in fishing.
2.) At present with the advancement of science it has become possible to generate electricity by harnessing the power of the tide.
3.) At high tide sea water is stored in salt pans from which salt is obtained.
4.) Tides help in coastal biodiversity and maintenance of mangroves.
5.) As a result of tide silt does not accumulate in the port.
12.) The time difference between two high tides is of ______________________________ .
A:- 12 hours and 25 minutes.
13.) What is waves ?
A:- An ocean wave is a movement of ssea water due to the effect of wind or an earthquake.
14.) How are ocean waves created?
A:- Ocean waves are created mainly by the friction of air currents with the water surface. This friction creates water pariticles in a circular orbit. Then the water particles follow that pat and move in the from of waves.
15.) The raised up portion of a wave is called ____________ and the depressed one is called ________________.
A:- Crest , trough
16.) What is amplitude ?
A:- The vertical distance between the crest and the trough is called the amplitude.
17.) What is wave length ?
A:- The distance between two successive creast or troughs is called wave length.