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Two conditions under which the work done is zero :

(i) when displacement = 0

(ii) when displacement is normal to the direction of force applied.

Single movable pulley has a mechanical advantage greater than one.

The mechanical advantage of a lever of the second order is always greater than one because its effort arm is always longer than the load arm i.e.

Effort arm > Load arm.

(i) The subjective property of sound related to its frequency is pitch.

(ii) The subjective property of light related to its wavelength is colour.

Refraction of light : The phenomenon in which a ray of light deviates from its original path while travelling from one optical medium to another medium having different optical density is called refraction of light.

Cause of refraction : Speed of light changes as it passes from one medium to another medium, therefore, light shows refraction.

The velocity of light in diamond is 2.42 times less than that in air.

It means that the ratio of speed of light in air to the speed of light in diamond is 2.42.

(i) The mass is measured by using a balance scale, beam balance or laboratory balance. An analytical balance is used to measure mass to a very high degree of precision. 

(ii) The weight is measured using a spring balance.

The nucleus of an atom becomes radioactive if the nucleus is large (i.e., atomic number > 82) or if the number of neutrons is much more than the number of protons.

(i) SI unit of work = Nm (Joule) 

CGS unit of work = dyne cm (erg) 

1 N = 10⁵ dyne

1 m = 10² cm

1 Joule = 10⁵ x 10² dyne cm = 10⁷ erg

(ii) W = F ·S = FS cos  θ

cos  θ maximum value 1 = FS

 θ =  0°

The outer and the inner surfaces of a calorimeter are polished, to prevent the transfer of heat by radiation.

The specific resistance of a material is the resistance of a wire of that material of unit length and unit area of cross-section. 

Its S.I. unit is ohm-metre (Ω m).

The two causes of energy loss in a transformer ate : 

(i) Energy loss due to induced (or eddy) currents in the core. 

(ii) Energy loss due to heat produced in coils (copper loss).

(i) The two methods of fishing are : 

1. Drifting 

2. Trawling

(ii) Kerala is the leading state for fish production in the western coast of India. The fishing industry has developed in India as it has a long, indented coastline dotted with a large number of lagoons and some of the coast remains calm for a long time which is quite convenient for fishing operations.

(a) NH₄OH + HCl ⟶ NH₄Cl + H₂O

(b) NaHSO₃ + HCl ⟶ NaCl + H₂O + SO₂

(c) Pb(NO₃)₂ +2HCl ⟶ PbCl₂ +2HNO₃

(d) Pb₃O₄ + 8HCl ⟶ 3PbCl₂ +4H₂O +Cl₂

(e) Zn+ 2HCl ⟶ ZnCl₂ + H₂

(f) Ca(HCO₃)₂ + 2HCl ⟶ CaCl₂+ 2H₂O + 2CO₂

1. Aluminium It is used for making pots, pans and parts of automobiles. 

2. Bhakra Nangal

1. It is used in power cables. 

2. It does not cause any pollution. 

It is a cheap source of energy. 

It prevents the loss of trees and manure due to burning of fuel wood and cow dung cakes. 

3. Manganese

Federal state is one that brings together a number of different political communities with a common government for common purposes, and separate “state” or “provincial” or “cantonal” governments for the specific needs of each community. USA is an example of Federal State. Quasi-federal state on the other hand refers to a union of states under a central government; rather ‘ than the individual governments of the separate states. India is by constitution a federal republic, but in reality functions as a quasi-federal state.

1. It is a clean energy resource. It is easy to transport through pipelines.

2. Bombay-High and Bassein.

1. These are renewable sources of energy, e.g., solar energy, wind energy. 

2. These do not cause any pollution.

1. It is the technique of increasing the recharge of ground water by capturing and storing rain water by constructing structures such as percolating pits, check dams, etc. 

2. 

(a) To overcome the inadequacy of surface water to meet our demands. 

(b) To check decline in ground water levels. 

(c) To enhance availability of ground water at specific place and time and utilize rain water for sustainable development. 

3. Surface runoff and Rooftop rain water harvesting.

1.

2. (i) Overpopulation or large and growing population can lead to water scarcity as more population means more demand for water. 

(ii) To facilitate higher foodgrain production, water resources are being over exploited to expand the irrigated areas and the dry season agriculture.

1. 1. Wells 2. Canals 3. Tanks 

2. Traditional means of irrigation like wells, canals and tanks are still important in most parts of India as these are cost effective methods whereas the modern methods like drip irrigation, sprinkle irrigation though save water but are very expensive.

1. Eastern slopes of Western Ghats. 

2. These forests provide teak, sal, sandalwood etc. which are used for furniture and other wood work.

• Forests provide many major and minor products like wood, gum, fibre, fruits etc. 

• They play a significant role in the prevention and control of soil erosion.

1. They are very dense. Transport is not possible. 

2. Ebony and Mahogany

(i) Annual range of temperature of station A is 5.6°C which is low because of the station is close to the sea. 

(ii) Station B has the lower organization because it is situated at greater altitude. 

(iii) Annual rainfall of station B is 31.8 cm.

Laterite Soil is formed by leaching in the regions of alternate wet and dry spells. 

Disadvantage—It is acidic is nature and cannot retain moisture.

(i) The North East Monsoons bring almost no rain to most of India because these winds have no moisture, as they blow from land to sea. 

(ii) ‘Mango showers’ are beneficial local winds because the little rainfall which they bringis important lor the growth ol mango, lea and coffee plants’m’Kera’la and the coasts of Karnataka. 

(iii) India stretchers over a large latitudinal extent is responsible for the climatic change and controls the climate all over India. Tropic of Cancer divides India into two heat zones, Tropical and Temperate zone. Peninsular India is in Tropical zone, this belt is close to equator and is also surrounded by water bodies so it has moderating affect of sea. But the northern part which is temperate zone has a different climate, because this belt is away from the equator and also away from the influence of sea, thus has extremes of climate. Its extremely high temperature in summer, attracts S.W. monsoon winds, thus is responsible for rains all over the country.

(i) The annual range of temperature of Station B is 5.6°C (30.0-24.4). 

(ii) The annual rainfall of Station A is 67.4 cm. 

(iii) ‘B’ is at the windward side of the Western Ghats as it is getting 50 to 61 cm of rainfall in the month of June and July whereas Station ‘A’ gets only 11.4 and 16.7 cm of rainfall in the same months, which shows that it lies on the leeward side of the mountain.

Two main features of the climate experienced by station A : 

(i) 1. The range of temperature is as high as (39°C – 20°C) = 19°C. 

2. The station receives rain from southwest monsoon.

(ii) 1552 mm.

(i) Climate : Rainfall and temperature influence the vegetation to a great extent. In India, regions receiving rainfall over 200 cm with high temperatures have tropical evergreen type of vegetation commonly. Regions with average temperature of 24° C 27°C and rainfall ranging between 150 cm 200 cm have tropical deciduous forests. Regions with moderate rain of 50 cm have thorn and scrub type of vegetation.

Tropical evergreen forests are not very important economically because : 

1. The trees are not found in pure stands thus, commercial exploitation proves to be very expensive. 

2. These are hardwood trees, i.e., they do not float on water.

3. Its warm and wet climate throughout the year paves way for a thick vegetation so, there is a lack of transport facilities. Thus, these forests do not encourage the exploitation economically.

(i) This is because of the moderating influence of the adjoining water bodies. The land and sea breezes moderate the temperatures. 

(ii) This is because Aravallis are parallel to the Arabian sea branch of S.W. monsoons and are unable to check the winds. This is also because Rajasthan lies in the rain shadow region when Bay of Bengal Branch strikes the Aravallis. 

(iii) Coromandel coast gets most of its rain during winter season because of N.E. monsoons which pickup moisture from Bay of Bengal and strikes the Coromandel coast.

(i) Driest month is March. 

(ii) Annual rainfall is 129.2 cms. 

(iii) Annual range of temperature is 12.1°C.

Regur soil is found in Gujarat and Maharastra. It helps agriculture because it is moisture retentive and rich in iron, potash, lime, calcium, magnesium and humus.

(i) Mean annual temperature – 28°C 

(ii) Total rainfall – 180.5 cm. 

(iii) Station has maritime type of climate because it has low range of temperature i.e., 6.6°C

(i) Annual range of temperature = 36.2 – 24.6 = 11.6°C. 

(ii) Total annual rainfall = 140.9 cm 

(iii) The station lies on the west coast of India because the amount of rainfall is high in the month of June and July.

(a) Laterite soil. Two states where this soil is found are Karnataka and Orissa. 

(b) Two characteristics of red soil are : 

(i) It does not retain water as it is porous. 

(ii) It is rich in iron but poor in nitrogen and phosphorus. 

(c) Soil conservation is an effort, made by man to prevent soil erosion to retain the fertility of soil. It aims at prevention as well as reclamation of soil that has been damaged by natural phenomena. 

Farming technique which help in soil conservation are : 

(i) Contour ploughing 

(ii) Terracing and contour bunding. 

(d) (i) Transported soil—When soil is carried from the place of its origin to another place by the agents of gradation such as river is called transported soil, e.g., Alluvial soil. 

(ii) In Situ—When the soil remains at the place of its origin it is called In situ. e.g. Black soil. 

(iii) Humus—The decomposed form of plant remains, animal manure and dead animals is called humus. It makes the soil fertile, porous and light.

Two reasons : 

(i) They are found in pure stands. 

(ii) They are not very dense therefore easily accessible.

Two advantages of surface wells over inundation canals are : 

1. They can be constructed where ever required. 

2. They supply water throughout the year.

(a) Tropical evergreen forests are difficult to exploit for commercial purposes because they are dense and found in mixed stands. 

(b) Two characteristics of tidal forests are : 

(i) They can grow in salty water. 

(ii) Trunks of these trees are supported by still like roots. 

(c) Three reasons why forests must be conserved are : 

(i) They help in preventing floods. 

(ii) They check soil erosion. 

(iii) They help to save the habitat of the wild animals. 

(d) Three trees found in monsoon deciduous forests are : Sal, Teak and Myrobalan.

 Uses: 

Sal: Its timber is useful for railway sleepers. 

Teak: Its timber is used for house construction and furniture. 

Myrobalan: Its fruit provide material for tanning leather.

(i) Laterite soil. 

(ii) Alluvial soil. 

(iii) Laterite soil.

Geographical reasons : 

(i) Different regions in India having different kinds of soil because different regions have different parent material and climatic conditions. 

(ii) Black soil is suitable for growth of cotten because it is moisture retentive and it is rich in iron, potash, lime, calcium, alumina humus etc. 

(iii) Afforestation or planting of tress saves the soil from erosion.

(a) Soil erosion caused by running water can be controlled by following methods : 

(i) By planting trees. 

(ii) Terrace farming. 

(b) Alluvial soil of the northern plains are coarse in texture and light in colour whereas the alluvial soil on the coastal plains are dark and fine in texture. 

(c) Three characteristics of black soil which make the soil fertile are : 

(i) It is rich in iron, potash, lime, calcium, alumina, magnesium, carbonates and humus. 

(ii) It is moisture retentive. 

(iii) It is fine grained in texture. 

(d) Geographical reasons: 

(i) Laterite soil is not suitable for cultivation because it is acidic in nature and does not retain moisture. 

(ii) Red soil is red in colour because it is rich in iron. 

(iii) Khadar soil is preferred to Bangar because it is more fertile as it is replished every year by floods.

Man having a box on his head who climbs up a slope does more work against the force of gravity because he has more potential energy by virtue of his position i.e.,height.

As, P. E. = Work done = F x S 

= mg x h

The two forces each of 5 N form a couple

∴ Moment of the couple = Either force x perpendicular distance between the two forces

= 5 x 1 

= 5 Nm (anti-clockwise)

(i) After the hail storm, ice absorbs heat energy required for melting from the surroundings, so the temperature of the surroundings fall further down and we feel cold. 

(ii) Heat is stored as latent heat which is used in the change of state of the substance.

(i) Victor Meyer’s test: Ethyl alcohol gives blood red colouration but sec-propyl alcohol gives deep blue colouration.

(ii) Acetic acid gives CO₂ gas (effervescence) with NaHCO₃ solution but acetaldehyde does not.

The school playground is out with bounds for the pupils of the primary school.