Given, relative density of wood
=0.6 = \(\cfrac { Density\quad of\quad wood }{ Density\quad of\quad water } =\cfrac { Density\quad of\quad wood }{ 10^{ 3 }kgm^{ -3 } } \)
\(\therefore\) Density of wood = 0.6 X 103 kg m^-3
Volume of wood = 2 X 0.25 X 0.10 m³ = 0.05 m³
As we know, mass of wooden block
= Density X Volume
= 0.6 X 10³ X 0.05 kg = 0.030 X 10³ kg

(i) A Healthy animal feeds regularly.
(ii) It has a normal posture.

(i) Smog: Smog is defined as fog intensified by atmospheric pollutants. A thick cloud of water droplets or smoke suspended in the atmosphere at or near the earth's surface restricting or obscuring visibility is called fog.
(ii) Two types of diseases caused-
(a) Allergies
(b) Heart diseases/cancer

(i) Disease cause damage to the health and functioning of body.Sometimes, diseases may cause irrecoverable damage to some part of body as a whole.
(ii) The patient is likely to be bedridden for sometimes as treatment of the disease may take sometime.During this period his work will suffer and some person is required to look after him.
(iii) The patient of infectious disease serves as a source of spreading infection to other healthy persons.

Earthquake produce low frequency infrasound before the main shock waves get set. These infrasonic waves are out of our audible range. But animals are able to detect these waves and hence some animals get disturbed before earthquakes and start behaving in a different manner.

Here displacement AB=2m is along the horizontal direction.
The gravitational force acts on the box in the vertically downward direction i.e., perpendicular to the direction of motion.Hence the work done by the gravitational force is zero.
\(W=F\ s\ cos\ 90°=0\)

Here, u = 0,a = 0.1 m \(s^{ 2 }\) t = 2 min = 120 s
(a) v = u + at = 0+0.1 x 120 = 12 m \(s^{ 1 }\)
(b) s = ut + \(\frac { 1 }{ 2 } at^{ 2 }=0x120+\frac { 1 }{ 2 } x0.1(120)^{ 2 }=\)  720 m

1. Organisms are classified in big groups first on the basis of independent characteristics.
2. The characteristic in the text level would be dependent on the previous one and would decide the variety of organisms in the next level.
3. Thus, one can build up a whole hierarchy of mutually related characteristics to be used for classification.

(i) A
(ii) D
(iii) B
(iv) C and E.

A molecule is usually formed when at leats two elements of the same or different kinds combine.If two or three atoms of the same kind of element combine, then it is referred to as molecule of an element or simply molecule.For example, molecule of oxygen is formed by the combination of two oxygen atoms.For example, a molecule or a compound of carbon dioxide is formed by the union of one carbon atom and two oxygen atoms.However, the noble gases consist of molecules of single atoms only.For example, helium exists as He.

A pure substance always has the same colour, taste or texture at a given temperature and pressure. Also it has fixed point or boiling point at constant pressure. Also it has a fixed melting point or boiling point at constant pressure. For example, pure water boils at 373k at 1 atmospheric pressure. But water containing some invisible dissolved substance boils at a temperature above 373k.

A gas is highly compressible and a large quantity of it can be compressed to a small manageable volume.Therefore, natural gas is compressed and is supplied for use by vehicles in the name of CNG(compressed natural gas)

Crop Rotation: The growing of different crops on the same field or a piece of land in a pre-planned succession is called crop rotation.
Selection of crops for crop rotation: Selection of crops depends on the -
(i) Moisture conditions i.e., availability water through rain or irrigation.
(ii) Length of rainy season.
(iii) Type of soil and nutrient status.
(iv) Availability of inputs-fertilisers, pesticides, manpower and machine power.
(v) Duration of crop-short or long.
(vi) Risk involved i.e., marketing and processing facilities.
For example, rabi crops of mustard, chickpea, linseed, barley, sunflower, and wheat are grown on conserved moisture.
In areas with assured soil moisture throughout the year, depending other inputs, rice, wheat, sugarcane, potato, and barseem are some of the major components of crop rotation.
Farmers near cities and towns prefer to grow vegetables and flowers for higher income.

(a) (1) Before selling of old fridge or AC to junk purchaser remove the CPC compressure Take care that its gas does not leak in the atmosphere
(2) While purchasing new air conditioner or refrigeration,keep in mind it is ozone friendly i.e..it should contain HFC (Hydro-fluro carbon) instead of CFC
(3) Many mattresses and pillows are made of chemicals which harm ozone, Beware of them and purchase only ozone friendly products.
(4) While purchasing room refreshers,paint,etc., check that they do not contain CFCs
(b) By organising campaigns on the above said point for protection of ozone layer amongst masses they depict the following values:
(1) Relationship of common man and community with the ozone layer.
(2) Environmental protection.

The factors which are important for maintaining good health  and if not present will lead to diseases are:
(i) Availability of proper balance diet (food) in sufficient quantity and clean water.
(ii) Good environment or surroundings that includes physical environment, Public cleanliness is important.Stagnation of dirty water, presence of open drains, garbage, in the surrounding cause spread of diseases.
(iii) Good special environment is an important factor is maintaining good health.If people mistreat each other or some particular people, they are mentally ill, they cannot lead happy life.
(iv) Good economic condition or job is the major factor which causes disease.For example, to provide good and proper food, clean clothes and hygienic conditions, proper social relationship, good economic conditions are essential.

Echo. Echo is the phenomenon of repetition of a sound due to its reflection from the surface of a large obstacle. When a loud sound is produced in an empty hall, the same sound is heard again after some time.
Conditions for the production of an echo:
(i) Sufficient time gap between original and reflected sounds. Due to persistence of hearing, we keep on hearing a sound for 0.1 s, even after reflected sound must reach the ear 0.1 s after the direct original sound.
(ii) Sufficient distance between the source of sound and the obstacle. The speed of sound in air is 344 m/s. The distance traveled by sound in\(0.1\quad s=344\times 0.1\times 0.1=34.4\quad m\) . So echo will be heard if the minimum distance between the source of sound and the obstacle =34.4/2=17.2 m.
(iii) Nature of the obstacle. For the formation of echo, the reflecting surface must be rigid such as a building, hill or cliff.
(iv) Size of the obstacle. Echoes can be heard if the size of the reflecting surface is quite large.

(a) Positive Work. Work done by a force is positive if the force acts in the direction of displacement.Then
\(W=F\times s\times cos\ 0°=F\ s\)
Examples:
(i) When a body falls freely under gravity, the work done by the force of gravity is positive.
(ii) When a horse pulls a cart, the applied force and displacement are in the same direction, the work done by the horse is positive.
(b) Negative Work. Work done by a force is negative if the force acts opposite to the direction of displacement.Then
\(W=F\times s\times cos\ 180°=F\ s(-1)=-F\ s\)
Examples:
(i) When a body is lifted up, the work done by the gravitational force is negative.This is because the gravitational acts vertically downwards while the displacement is in the vertically upward direction.
(ii) When brakes are applied to a moving vehicle, the work done by the braking forces is negative.The braking force acts in the backward direction while the displacement of the vehicle is in the forward direction.

Difference between mass and weight:

Mass	Weight
1. Mass is the quantity of matter contained in a body and is the measure of its inertia.	Weight of a body is the force which a body is attracted towards the centre of the earth.
2. Its value remains constant at all places.	Its value (W=mg) changes from place to place due to the change in the value of acceleration due to gravity 'g'.
3. It is a scalar quantity.	It is a vector quantity.
4. It is measured by a pan balance.	It is measured by a spring balance.
5. Mass of a body is never zero.	Weight of a  body is zero at the centre of the earth because there 'g' becomes zero.
6. Its unit is kg	Its unit is Newton or kg-wt.

Newton's first law of motion. According to this law, a body at rest or in uniform motion will remain at rest or in uniform motion unless an unbalanced force acts upon it. This law consists of three parts:
(i) First part, says that a body at rest continues in its state of rest. For example, a person standing in a bus falls backward when the bus suddenly starts moving forward. When the bus moves, the lower part of his body begins to move along with the bus while the upper part of his body continues to remain at rest due to inertia. That is why a person falls backward when the bus starts.
(ii) Second part, says that a body uniform motion continues moving in straight line path will a uniform speed. for example, when a moving bus suddenly stops, a person sittng in it falls forward. As the bus stops, the lower part of his body comes to rest along with the bus while upper part of his body continues to remain in motion due to inertia and so he fall forward.
(iii) Third part, says that a body moving with a uniform speed in a straight line cannot change itself its direction of motion. For example, when a bus takes a sharp turn, a person sitting in the bus gets a force acting away from the center of the curved path due to his tendency to move in the original direction. He has to hold on a support to prevent himself from swaying away in the turning bus.

The practice of naming is one of the greatest inventions of man. Millions of animals and plants are named differently in different languages in different parts of the world. It means the names used for one organism differs from place to place. For example, Argemone a common weed has as many as ten to twele Hindi names alone. Some call it 'Firangi Dhatura', Sial Kanta', 'Pila Dhatura', 'Bharband', 'Kandhari', 'Satya nasi buti', 'Katela', 'Jahriber', 'Ugar Kanta' etc. Same thing is applicable to animals and other plants. Sometimes the common names are misleading. Same name may be used for different organisms in different parts.
To avoid this confusion Linnaeus gave a system in which an organism is given a name with two components-the first part is the generic name and the second part is the specific name. Thus the scientific name of common cat is Felis domestica, and that of tiger is Felis tigris. This system of giving a name with two components to an organism is called 'Binomial system of nomenclature'. The scientific names thus given to the organism are recognized all over the world. Hence, confusion is avoided on this aspect.

(i) We will give ORS (Oral Rehydration Solution) from time to time till we reach to doctor or doctor comes to attend the patient. ORS is available in powder form packed in sachets.
(ii) We can make ORS in home by the following way:
Ingredients
1. One level teaspoon of salt
2. Eight level teaspoon of sugar
3. One litre of clean drinking or boiled water and then cooled (5 cupfuls-each cup about 200 .ml.),
Preparation Method
Stir the mixture till the salt and sugar dissolve.
(a) Arrange community lectures, debates to sensitise harmful effects of dehydration of the body.
(b) Conveying importation of ORS and its preparation in home

Compound name	chemical name	chemical formulae
Banking soda	Sodium bicarbonate	NaHCO3
washing soda	Sodium carbonate	Na2CO3.10H2O
blue vitriol	Copper sulphate	CuSO4.5H2O
green vitriol	Ferrous sulphate	FeSO4.7H2O
gypsum	Calcium sulphate	CaSO4.2HO
oil of vitriol or white vitriol	Sulphuric acid	H2SO4
soda ash	Sodium carbonate	Na2CO3
marble chips	Calcium carbonate	CaCO3
lime water	Calcium hydroxide	Ca(OH)2

Comparison of properties of true solution, colloidal solution, and suspension

Property	True solution	Colloidal solution	Suspension
(1) Appearance	homogeneous and transparent	Heterogeneous and translucent	heterogeneous and opaque
(2) particle size	< 1 nm (10-7 cm)	1 nm - 100 nm	> 100 nm (10-5 cm)
(3) Visibility	particles are not visible even with a powerful microscope	Particles can be seen with a high power microscope	particles can be seen with naked eyes
(4) Stability	Stable	Stable	Unstable
(5) Diffusion	Diffuse rapidly	Diffuse slowly	Do not diffuse
(6) Filterability	Pass through filter paper	passes through filter paper	can be separated by filter paper
Example	NaCI dissolved in water	Blood	Mud water.

Test of a colloidal solution or a suspension.
(i) A colloidal solution is turbid and the particle settles down on adding salt. In a suspension, particles settle down on keeping under the influences of gravity.
(ii) If the particles in a heterogeneous and opaque solution can be seen with naked eyes and get settled on keeping, then it is a suspension.

The smell of hot sizzling food reaches us several metres away because food particles diffuse faster in air when hot and we smell it in no time whereas cold food particles would take a long time to diffuse and we have to go close to have a smell of it.

No, it is not necessary that their weights in air should also be the same. This is because the two bodies have undergone the same loss in weight on completely immersing in water due to their equal volumes, not due to their equal weights. So, they may have different weights in air.

Nutrients supplied by air, water and soil

No.	Source	Nutrients
1.	Air	Carbon (in the form of CO2), oxygen by exchange of gas through  stomata.
2.	Water	Hydrogen (in the form )
3.	Soil	(i) Macro-nutrients  Nitrogen, Phosphorus, Potassium, Sulphur, Calcium, Magnesium.  (ii) Micro-nutrients  Iron, Manganese, Boron, Zinc, Copper, Molybdenum, Chlorine.

Organism	Role/Activity
(i) Rhizobium and blue-green algae	Nitrogen fixation
(ii) Bacteria and Fungi	Ammonification (Organic Nitrogen \(\rightarrow\)Ammonia)
(iii) Nitrobactor and Nitrosomonas (Nitrifying bacteria)	Nitrification (Ammonia \(\rightarrow\) Nitrites) (Nitrites \(\rightarrow\) Nitrates)
(iv) Pseudomonas (Denitrifying bacteria)	Denitrification (Nitrates \(\rightarrow\) Free nitrogen)

Three times in the last year. Names of disease - malaria, dysentery, viral fever.
Change in habit
(i) avoiding accumulation of stagnant water to avoid mosquito breeding.
(ii) use of spray and other measures to kill mosquitoes.
(iii) Keeping the surrounding clean.
(iv) use of nourishing food and safe water. Avoiding exposed food and unfiltered water.
(v) personal hygiene.
(b) One change in surroundings: Avoiding accumulation of garbage and stagnant water in the surroundings.

Here,   \(m_1 = 1 \ kg,\)    \(u_2= 10 \ ms^{-1},\)   \(m_2 = 5 \ kg,\)   \(u_2=0\)
Let v be the velocity of the combined object after the collision
Total momentum just before the impact
 \(=m_1u_1+m_2u_2 = 1 \times 10 +5 \times 0 = 10\quad kg \quad ms^{-1}\)
Total momentum just after the impact
 \(= (m_1+m_2)v=(1+5)v=6 v \quad kg m s^{-1}\)
By conservation of momentum,
6v = 10
or    \(v = \frac {10}{6}=\frac {5}{3} m s^{-1}\)
\(\therefore\)   Total momentum just after the impact
 \(= 6 \times \frac {5}{3}=10 \quad m s^{-1}.\)

Different types of Motions:
1.Translatory Motion When a body moves as a whole along a straight or curved path, it is said to be in translatory motion.It is again of two types:
(i) Rectilinear motion Here a body moves as a whole along a straight path.For example a train moving on straight rails has translatory rectilinear motion.
(ii) Curvilinear motion.Here a body moves as a whole along a curved path For example motion of a bicycle taking a turn along a curved path.
2.Rotatory motion.When a body rotates about a fixed point or axis , it has rotatory motion For example motion of a flywheel about a shaft.
3.Vibratory or oscillatory motion. When a body moves to and from about a mean position again and again it has vibratory or oscillatory motion For example the motion of the pendulum of a wall clock. 
4.Complex motion. Sometimes ,the motion of a body may be a combination of more than one types of motion For example a ball rolling down an inclined plane has botth translatoruy and rotatory motions.

In spite of certain external differences, plants and animals show a number of very obvious similarities which are as follows:
(i) Plants and animals are made up of microscopic units-the cell.
(ii) Both contain living substance protoplasm.
(iii) Certain life processes i.e., respiration, digestion, reproduction, assimilation etc. take place in both the groups in identical manner.
 (iv) Both show response to external stimuli.
(v) They both show growth.
(vi) Both reproduce and pass on their hereditary characters to the offspring by the same mechanism.

(i) Difference between Meristematic cells and Permanent cells

Meristematic Cells	Permanent Cells
1. They have dense cytoplasm and a large centrally placed nucleus.	1. They have a large central vacuole, and normal nucleus.
2. These cells are capable of dividing to produce new cells.	2. They attain permanent shape and are not capable of producing new cells.

(ii) Difference between Parenchyma and Collenchyma

Parenchyma	Collenchyma
1. It is living and mainly storage tissue.	1. It is living and mainly provides tensile strength to stem and leaf stalk.
2. Parenchymatous cells have large intercellular spaces. Their walls do not have thickening at the corners.	2. Collenchymatous cells have very little intercellular spaces. They have thickening at the corners of cell walls.

Isotopes have the following uses:
(i)Treatment of diseases-Radioactive isotopes are used for the treatment of dreadful diseases like cancer.Cobalt-60 is used ti kill malignant cells in patients suffering from cancer.
(ii)Radioactive isotopes are used in chemical analysis.
(iii)Diseases in plants are investigated by using radioactive isotopes.
(iv)Production of energy: Uranium-235 can be subjected to fission process and thus production of electricity.
(v)Dating of plants, animals/humans beings obtained from ancient times after excavation by using carbon-14
(vi)I-131 is used in the treatment of thyroid disorders.
(vii)P-32 is used in the treatment of leukemia.

Homogeneous mixture Heterogeneous mixture (i) it has no visible boundary or boundaries of separation between its constituents. (i) It has visible boundary/boundaries of separation between its constituents. (ii) It has a uniform composition throughout its mass. (ii) The composition of the mixture varies from mass to mass (iii) It does not show the Tyndall effect (iii) It shows the Tyndall effect.

The specific function of cardiac muscle is to contract and relax rhythmically throughout life.

(i) The relative density of a substance is the ratio of its density to that of water.
Relative density of a substance
= \(\cfrac { Density\quad of\quad the\quad substance }{ Density\quad of\quad water } \)
Relative density of a substance
=\(=\cfrac { Mass\quad of\quad the\quad substance }{ Volume\quad of\quad the\quad substance } \times \cfrac { Volume\quad of\quad water }{ Mass\quad of\quad water } \)  \(\left[ \therefore Density=\cfrac { mass }{ volume } \right] \)
Given that, mass of the cube = 50 g
Side of cube = 1.5 cm
\(\therefore\) Volume of cube = (1.5)³ cm³ = 3.375 cm³
\(\therefore\) Density =\(\cfrac { mass }{ Volume } \)
=\(\cfrac { 50 }{ 3.375 } \) = 14.81 g cm^-3
(iil) Given that, mass, m = 250 g
Volume, V= 400 cc
\(\therefore \) Density=\(\cfrac { mass }{ Volume } \)
= \(\cfrac { 250 }{ 400 } \)g(cc)^-1= 0.625 g (cc)^-1
As we know that, density of water = 1 g (cc)^-1. So, density of tin is less than that of water and hence tin will float.

\(v_{ av }=\frac { s_{ 1 }+s_{ 2 } }{ t_{ 1 }+t_{ 2 } } =\frac { s }{ \frac { s_{ 1 } }{ v_{ 2 } } +\frac { s_{ 2 } }{ v_{ 2 } } } \)
\(40=\frac { 100 }{ \frac { 30 }{ 30 } +\frac { 70 }{ v_{ 2 } } } \)
\(=1+\frac { 70 }{ v_{ 2 } } =\frac { 100 }{ 40 } =\frac { 5 }{ 2 } \)
\(\frac { 7 }{ v_{ 2 } } =\frac { 5 }{ 2 } -1=\frac { 3 }{ 2 } \)
\(v_{ 2 }=\frac { 7X2 }{ 3 } =\frac { 14 }{ 3 } =4.67\quad km\quad h^{ -1 }\)