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Page No 262:

Question 1:

Give one advantage of artificial insemination.

Answer:

One of the most important benefit of artificial insemination is that it reduces the spreading of diseases in cattles.

Page No 262:

Question 2:

Name the nucleic acids that are present in an animal cell.

Answer:

In an animal cell, Deoxy Ribonucleic Acid (DNA) and Ribonucleic Acid (RNA) are found.

Page No 262:

Question 3:

What is the difference between uniform linear motion and uniform circular motion? Explain with examples.

Answer:

When a body travels equal distances in equal intervals of time along a straight line, the motion of the body is said to be Uniform linear motion. But, when a body travels equal distances in equal intervals of time along a circular path, then the motion of the body is said to be Uniform circular motion. The main differences between Uniform linear motion and uniform circular motion are given below:

Uniform linear motion:
Example: A car moving with a constant speed along a straight road.

Uniform circular motion:
Example: A car moving on a circular track with constant speed.
 

Page No 262:

Question 4:

Explain the term 'amplitude' of a wave. Draw the diagram of a wave and mark its amplitude on it.

Answer:

When a wave travels through a medium, it disturbs the particles of the medium. The maximum displacement of the particles of the medium from their mean position is known as the amplitude of the wave. 

The diagram below shows the amplitude of a wave: 

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Question 5:

Define: (i) Hypertonic solution (ii) Hypotonic solution

Answer:

(i) Hypertonic solution: A solution having a higher concentration of solute outside as compared to outside the cell is called hypertonic solution. In a hypertonic solution, a cell progressively loses water through exosmosis.

(ii) Hypotonic solution: A solution having a lesser concentration of solute inside as compared to outside the cell is called a hypotonic solution. In a hypotonic solution, a cell progressively gains water through endosmosis.

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Question 6:

Explain why:
(a) air is used to inflate tyres.
(b) steel is used to make railway lines.

Answer:

(a) Air is highly compressible, so when air is filled in the tyres, it provides damping and adjusts easily to get the required friction depending upon the surface conditions.

(b) Steel is used for railway lines because it has high tensile strength and appropriate hardness. It has resistance to internal and surface cracks.

Page No 262:

Question 7:

What is meant by atomicity? Explain with two examples.

Answer:

Atomicity is the number of atoms of an element present in one molecule of that element. For eg. Atomicity of oxygen(O2) is 2, Atomicity of ozone(O3) is 3.

Page No 262:

Question 8:

From the symbol 31P15, state:
(i) mass number of phosphorous,
(ii) atomic number of phosphorous, and
(iii) electron configuration of phosphorus.

Answer:

(i) The mass number is always represented in superscript.
So, the mass number of phosphorous = 31

(ii) The atomic number is always represented by subscript 
So, the atomic number of phosphorous = 15

(iii) Electronic configuration of phosphorous = 2, 8, 5
 

Page No 262:

Question 9:

State whether the following statements are true or false:
(a) A falling stone also attracts the earth.
(b) The force of gravitation between two objects depends on the nature of the medium between them.
(c) The weight of an object on the earth is about one-sixth of its weight on the moon.

Answer:

(a) The given statement is true. A falling stone attracts the earth with the same force earth attracts the stone, but as the mass of the earth is much much higher as compared to the stone, so the effect of the force is negligible. 

(b) The given statement is false. Because the force of gravitation between two objects depends only on the masses of the objects and the distance between them. The change of the medium does not affect the value of the gravitational force.

(c) The given statement is false. The weight of an object is basically due to the acceleration due to gravity or the gravitational force by the planet. The value of acceleration due to gravity on the moon is one-sixth of the value on the earth. Hence, the weight of an object on the moon is about one-sixth of its weight on the earth. 

 



Page No 263:

Question 10:

Give one example each in which a force does
(a) positive work
(b) negative work, and
(c) zero work.

Answer:

(a) When the body is displaced in the direction of the applied force, then the work is said to be positive work. Example: When a boy pushes a box forward by applying a force, the work done is positive.

(b) When a body is displaced in the opposite direction of the applied force, then the work done is said to be negative work. Example: When a boy takes a bag full of sand up to a height 'h', then the work done by the force of gravity is negative work. 

(c) When the displacement of the body is zero then the work done by the applied on the object is said to be zero. Example: When a boy pushes a wall and the wall does not move, then the work done by the boy is zero. 

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Question 11:

When we open a gas tap for a few seconds, the sound of escaping gas is heard first but the smell of gas comes later. Why?

Answer:

We know that the speed of sound is faster than the speed of gas molecules. Therefore when we open the gas tap, sound comes first due to the fast movement of gas particles against air friction and collision. The gas-particle reaches to our nose later.  

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Question 12:

(a) Name and draw a cell which does not have a well defined nuclear region. Label any four parts.
(b) Mention two ways by which a photosynthesising cell belonging to this group differs from a cell of your body.

Answer:

(a) Cells that do not possess a well defined nucleus are called prokaryotc cells. A typical prokaryotic cell can be represented as follows:


(b)  The difference between a photosynthetic prokaryotic cell and a human cell are as follows:
 

Photosynthetic prokaryotic cell Human
1. Photosynthetic pigments are enclosed in membranous structures. 1. Photosynthetic pigments are not present.
2. Cell is present across the cell membrane. 2. Cell wall is absent.
3. Nucleoid is present instead of nucleus. 3. A well defined nucleus is present.

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Question 13:

What are the major divisions in the Plantae? What is the basis of this division?

Answer:

The major divisions in kingdom plantae are as follows:


The different divisions of kingdom plantae are classified on the basis of following criteria:

  • The first level of classification is based on whether the plant has a well-defined and distinct components.
  • The second level of classification is based on presence of vascular tissues.
  • The third level of classification is based on the ability of the plant to produce seeds and whether the seeds are enclosed within the fruits.

Page No 263:

Question 14:

In a cluster of hutments, many people are suffering from malaria. Mention the unhygienic conditions that must be prevailing in that locality. How does a doctor confirm malaria?

Answer:

The unhygienic conditions that lead to malaria in a cluster of hutments are as follows:
1. Stagnant water may be present in the vicinity of the hutments which can serve as breeding ground for mosquitoes.
2. The sewage drains may be open which can lead to uncontrolled growth of mosquitoes.
3. Undulating surface of the canvas sheet which are generally used in hutments, hold rainwater that contributes to the growth of mosquitoes. 

A doctor can confirm malaria by performing a blood test to detect the malarial parasite.

Malaria can be prevented by taking the following measures:
1. Breeding grounds such as swamps and puddles should be destroyed.
2. Insect repellents can be used to reduce mosquito bites.
3. Chemical insecticides can be used to kill mosquitoes.

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Question 15:

How is soil formed?

Answer:

The formation of soil is influenced by the processes of weathering and paedogenesis. In weathering, bigger rocks breakdown into small fine particles of soil. This process can be induced by chemical, biological or physical processes. The uneven heating and contraction of rocks because of temperature differences during day and night is one of the major reason for breakdown of rocks.
In paedogenesis, the organic material is decomposed by the living organism to form soil. This process involves mineralisation and humidification of the organic matter.

Page No 263:

Question 16:

(a) Compare the properties of solids, liquids and gases in tabular form.
​(b) Give two reasons for saying that wood is a solid.

Answer:

(a)
 

Property Solid Liquid Gas
Packing of particles Particles are packed very close to each other. Particles are packed less close to each other. Particles are packed very far from each other.
Force of attraction between the particles Strongest Weaker than solids. Negligible
Shape and volume Fixed shape and volume. No fixed shape but fixed volume. Neither fixed shape nor fixed volume.
Compressibility Negligible. Higher than solids. Highest.
Rate of diffusion Very low Higher than solids. Highest.

(b) Wood is solid because:
(i) It has a fixed shape and volume.
(ii) It cannot be compressed.
 

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Question 17:

(a) What are the three general classes of matter? Give one example of each type.
​(b) Draw a flow-chart for the schematic representation of different types of matter.

Answer:

(a) Three general classes of matter are:
(i) Solid: They have fixed shape and volume. For eg. wood, stone, etc.
(ii) Liquid: They have fixed volume but do not have a fixed shape. For eg. alcohol, milk, etc.
(iii) Gas: They neither have fixed shape nor fixed volume. For eg. oxygen, hydrogen, etc.

(b)  Schematic diagram showing different types of matter:


 

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Question 18:

(a) What is the difference between 'distance travelled' by a body and its 'displacement'? Explain with the help of a diagram.
​(b) An ant travels a distance of 8 cm from P to Q and then moves a distance of 6 cm at right angles to PQ. Find its resultant displacement.

Answer:

(a) When a body moves from a point to another, then the total path length covered by the body is known as the distance travelled by the body, whereas the shortest distance or pathlength between the initial point of motion and final point of the motion is referred to displacement. Distance is a scalar quantity but the displacement is a vector quantity. 



As you can see in the figure, the pathlength ABCDE is the distance travelled by the body, whereas the shortest path AE between the initial and final position is the displacement. 

(b)
 

Let the body travels to point R, 6 cm farther from point Q at a right angle to the PQ. Then, PQR is a right triangle. 

(PQ)2+(QR)2=(PR)282+62=(PR)2(PR)2=64 + 36 = 100PR = 10 cm

Hence, the resultant displacement of the Ant is 10 cm from the initial position.
 



Page No 264:

Question 19:

Give one example each where:
(a) a force moves a stationary body.
(b) a force stops a moving body.
(c) a force changes the speed of a moving body.
(d) a force changes the direction of a moving body.
​(e) a force changes the shape (and size) of a body.

Answer:

(a) If we push a stationary box lying on the ground, then the box starts moving due to the action of the force.

(b) When we apply the brakes in a car, a force stops the motion of the car.

(c) If we hit a ball lying on the ground by a force, then the ball starts moving. In this case, the force changed the speed of the ball from zero to a certain value.

(d) When we tie a stone with a thread and move it around us on a circular path, then the force exerted by our hands works as a centripetal force. That force helps the stone to change its direction continuously and move on a circular path.

(e) When we blow air into a balloon, force changes the size and when we squeeze a rubber ball, the force changes the shape of the ball.
 

Page No 264:

Question 20:

Draw a well labelled diagram of animal cell and mention one function of the main cell organelles.

Answer:

The diagram of an animal cell is as follows:


A typical animal cell is composed of nucleus, mitochondrion, Golgi body, and rough  endoplasmic reticuclum (RER).

The different functions of the major cellular organelles are as follows:

  • Nucleus regulates all the metabolic and fundamental processes in a cell.
  • Mitochondrion is responsible for the synthesis of Adenosine Triphosphate (ATP) in the cell.
  • RER acts as the site for the synthesis of proteins.

Page No 264:

Question 21:

What are meristematic tissues? Explain with the help of suitable diagram. Give their classification on the basis of their position in the plant body.

Answer:

Meristematic tissues are formed by cells which show continuous division. These tissues are responsible for increasing the length as well as the birth of a plant. 

Figure. 1. Different types of meristematic tissues.

Meristematic tissues are categorized into three types on the basis of their position in the plant. These are as follows:

(i) Apical meristem: These meristematic tissues are present at the growing tips of roots and stems, which constitute the shoot apex. These tissues are also present in the apical regions of the leaves.

(ii) Intercalary meristems: These meristematic tissues are found at the bases of leaves or internodes. In many cases, these tissues can also be found below the nodes.

(iii) Lateral meristems: These tissues are present below the cork cambium and can also be found in vascular cambium as well as vascular bundles of dicot roots.

Page No 264:

Question 22:

Which contains more heat, 1 kg of ice at 0° C or 1 kg of water at 0° C? Give reason for your answer.

Answer:

1 kg of water has more heat than 1 kg of ice.
To heat 1 kg of ice from 10 °C to 30 °C takes 83.6 kJ.
To melt ice and to raise its temperature by 20 °C, it takes 333.5 kJ for ice to melt and 83.5 kJ to increase the temperature by 20 °C, so total 427.15 kJ heat is required.
So, 1 kg of ice needs more energy to reach a temperature equal to 1 kg of water.

 

Page No 264:

Question 23:

21.5 g of sodium chloride dissolves in 60 g of water at 25° C. Calculate the solubility of sodium chloride in water at that temperature.

Answer:

Solubility of a solute=Weight of solute in saturted solutionWeight of solvent in saturated solution×100Solubility of a solute=21.560×100Solubility of a solute=35.833 g/100 mL of water
As water has a density 1 g/cc solubility is expressed as 35.833 g/100 mL of water.

Page No 264:

Question 24:

A bus running at a speed of 18 km/h is stopped in 2.5 seconds by applying brakes. Calculate the retardation produced.

Answer:

Negative acceleration is known as the retardation. 

The initial speed of the bus = 18 km/h

Final speed of the bus = 0 

Time taken to stop the bus = 2.5 s

Acceleration of the body =Final speed - Initial speedTime Taken

Acceleration=0-18×1000 m3600 s2.5 s=-2 m/s2

Hence, retardation produced is 2 m/s2.

Page No 264:

Question 25:

Why are road accidents at high speeds very much worse than road accidents at low speeds?

Answer:

When road accidents happen at very high speeds, a larger change in momentum occurs in a very short span of time. Due to that larger forces are created and the chances of damage increase to the maximum. Whereas, when accidents happen at low speeds, the change in momentum is low. That's why the forces involved are small, which cause less damage.

Page No 264:

Question 26:

In brief state what happen when
(a) Dry apricot is left for sometime in pure water and later transferred to sugar solution.
​(b) A red blood cell is kept in concentrated salt solution.

Answer:

(a) When dry apricots are left in pure water, the water will enter into the apricots, which will result in swelling of the apricots. These apricots will gradually lose water and shrink when they are transferred to a sugar solution.

(b) A red blood cell kept in concentrated salt solution will lose water due to exosmosis and will shrink in size.

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Question 27:

While walking through garden, Kapil plucked the tips of some flowering plants. Gardner saw him doing this and persuaded him not to do so as it is not good for plant growth.
(i) What happens to the plants if their tips are removed?
​(ii) What are meristems?

Answer:

(i) Tips contain apical meristem, which are responsible for the growth of the plant. In case the tips of the plants are removed, the growth of the plant will be severely affected.

(ii) Meristems are rapidly proliferating cells, which help in the growth of the plant. These cells are non-differentiated and give rise to different tissues of the plant.



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