What are the different means by which infectious diseases are spread?
Infectious diseases can be spread in several ways such as air, water, sexual contact, blood, and vectors.
(i) Through Air: Sneezing or coughing little droplets thrown in the air carry microbes which can cause the spread. For example, tuberculosis, pneumonia, etc. spread through air.
(ii) Sometimes causal micro-organisms get mixed with drinking water and spread water borne diseases. Cholera for example is water borne disease.
(iii) Sexual Contact: Diseases such as syphilis or AIDS are transmitted by sexual contact.
(iv) Certain diseases such as AIDS can spread via blood to blood contact during blood transfusion or pregnancy.
(v) Through vectors : These are intermediaries which carry the infectious agents from the patient to the host. For example mosquitoes spread malaria.
Popular Questions of Class 9 Science
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Abdul, while driving to school, computes the average speed for his trip to be 20 km h-1. On his return trip along the same route, there is less traffic and the average speed is 40 km h-1. What is the average speed for Abdul’s trip?
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An object of mass 40 kg is raised to a height of 5 m above the ground. What is its potential energy? If the object is allowed to fall, find its kinetic energy when it is half-way down.
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A driver of a car travelling at 52 km h-1 applies the brakes and accelerates uniformly in the opposite direction. The car stops in 5 s. Another driver going at 3 km h-1 in another car applies his brakes slowly and stops in 10 s. On the same graph paper, plot the speed versus time graphs for the two cars. Which of the two cars travelled farther after the brakes were applied?
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Fig 8.11 shows the distance-time graph of three objects A,B and C. Study the graph and answer the following questions:
Fig. 8.11
(a) Which of the three is travelling the fastest?
(b) Are all three ever at the same point on the road?
(c) How far has C travelled when B passes A?
(d) How far has B travelled by the time it passes C? - Q:-
Two objects, each of mass 1.5 kg, are moving in the same straight line but in opposite directions. The velocity of each object is 2.5 m s-1 before the collision during which they stick together. What will be the velocity of the combined object after collision?
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Soni says that the acceleration in an object could be zero even when several forces are acting on it. Do you agree with her? Why?
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Two objects of masses 100 g and 200 g are moving along the same line and direction with velocities of 2 m s-1 and 1 m s-1, respectively. They collide and after the collision, the first object moves at a velocity of 1.67 m s-1. Determine the velocity of the second object.
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How do poriferan animals differ from coelenterate animals?
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The speed-time graph for a car is shown is Fig. 8.12.
Fig. 8.12
(a) Find how far does the car travel in the first 4 seconds. Shade the area on the graph that represents the distance travelled by the car during the period.
(b) Which part of the graph represents uniform motion of the car? - Q:-
How are sol, solution and suspension different from each other?
Recently Viewed Questions of Class 9 Science
- Q:-
Complete the following table.
Atomic
NumberMass
NumberNumber
of
NeutronsNumber
of
ProtonsNumber
of
ElectronsName of
the Atomic
Species9 - 10 - - - 16 32 - - - Sulphur - 24 - 12 - - - 2 - 1 - - - 1 0 1 0 - - Q:-
A freely falling object eventually stops on reaching the ground. What happenes to its kinetic energy?
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A doctor/nurse/health-worker is exposed to more sick people than others in the community. Find out how she/he avoids getting sick herself/himself.
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A battery lights a bulb. Describe the energy changes involved in the process.
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The volume of 50 g of a substance is 20 cm3. If the density of water is 1 g cm-3, will the substance float or sink?
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On the basis of Rutherford’s model of an atom, which sub-atomic particle is present in the nucleus of an atom?
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Explain, why is it difficult for a fireman to hold a hose, which ejects large amounts of water at a high velocity.
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A hammer of mass 500 g, moving at 50 m s-1, strikes a nail. The nail stops the hammer in a very short time of 0.01 s. What is the force of the nail on the hammer?
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Write the steps you would use for making tea. Use the words solution, solvent, solute, dissolve, soluble, insoluble, filtrate and residue.
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A stone is thrown vertically upward with an initial velocity of 40 m/s. Taking g = 10 m/s2, find the maximum height reached by the stone. What is the net displacement and the total distance covered by the stone?
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