Q35 of 805 Page 156

Explain giving reasons

(a) Balanced diet is necessary for maintaining healthy body.


(b) Health of an organism depends upon the surrounding environmental conditions.


(c) Our surrounding area should be free of stagnant water.


(d) Social harmony and good economic conditions are necessary for good health.


OR


Why is AIDS considered to be a ‘Syndrome’ and not a disease?

a) Food is essential for growth, development and maintenance of the body. A balanced diet provides raw material in the form of proteins, carbohydrates, fats, vitamins, minerals, roughage etc. in appropriate amount for proper growth and functioning of body.


b) According to WHO (World Health Organization) “health is a state of complete physical, mental and social well being and not merely an absence of disease”. Thus surrounding environmental conditions play an important role in an individual’s health. If the surrounding is not kept clean we are much likely to fall ill.


c) Stagnant water is the major source of water borne diseases and breeding site for mosquitoes. Mosquitoes are vectors for many diseases like malaria, dengue etc., and flourish in stagnant water. Hence, our surrounding should be free of stagnant water.


d) Social harmony and good economic conditions are necessary for good social and mental health. In a harmonious society a person can grow and develop more. Further adequate earning is necessary for being able to get balanced diet and better living conditions.


OR


Syndrome is any disease, disorder or improper function characterized by more than one symptom. AIDS is caused by HIV virus.


Thus, the virus damages the immune system of the body. Due to this the body can no longer fight off the many minor infections. Instead, every small cold ca become pneumonia or minor gut infection can become severe diarrhea with blood loss. The effect of disease can become very severe and complex and can kill a person suffering from it. Hence there is specific symptom of AIDS but it results in complex diseases ad symptoms. Thus called syndrome.


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The mass of one steel screw is 4.11g. Find the mass of one mole of these steel screws. Compare this value with the mass of the Earth (5.98 × 1024kg). Which one of the two is heavier and by how many times?

OR


In photosynthesis, 6 molecules of carbon dioxide combine with an equal number of water molecules through a complex series of reactions to give a molecule of glucose having a molecular formula C6H12O6. How many grams of water would be required to produce 18 g of glucose? Compute the volume of water so consumed assuming the density of water to be 1 g cm–3.

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(a) Explain the meaning of inertia with the help of an example.

(b) Two balls of same size but of different materials, rubber and iron are kept on the smooth floor of a moving train. The brakes are applied suddenly to stop the train. Will the balls start rolling? If so, in which direction? Will they move with the same speed? Give reasons for your answer.


OR


(a) A ball of mass m is thrown vertically upward from the ground with an initial speed v, its speed decreases continuously till it becomes zero. Thereafter, the ball begins to fall downward and attains the speed v again before striking the ground. It implies that the magnitude of initial and final momentum of the ball are same. Yet, it is not an example of conservation of momentum. Explain why?


(b) A bullet of mass 20 g is horizontally fired with a velocity 150 m s–1 from a pistol of mass 2 kg. What is the recoil velocity of the pistol?

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(a) With the help of Second Law of Motion and the Universal Law of Gravitation derive an expression for acceleration due to gravity ‘g’.

(b) The weight of any person on the moon is about 1/6 times that on the earth. He can lift a mass of 15 kg on the earth. What will be the maximum, mass, which can be lifted by the same force applied by the person on the moon?


OR


(a) Identical packets are dropped from two aeroplanes, one above the equator and the other above the north pole, both at height ‘h’. Assuming all conditions are identical, will these packets take same time to reach the surface of the earth? Justify your answer.


(b) It is seen that a falling apple is attracted towards the earth. Does the apple also attract the earth? If so, we do not see the earth moving towards the apple. Why?