Practice 1. A car travels 600 m in 30 s. what is its average speed? Why is its actual speed usually different from its average s
peed? 2. A car has a steady speed of 8 m/s. a) how far does the car travels in 8 s? b) how long does the car take to travel 160 m? 3. A bus has an acceleration of +2 m/s?. what does this tell you about the velocity of the car? What is meant by an acceleration of -2 m/s2 4. An aircraft on its take-off run has a steady acceleration of 3 m/s2 a) what velocity does the aircraft gain in 4 s? b) if the aircraft passes one post on the runway at a velocity of 20 m/s, what is its velocity 8 s later?
Ans. (1) For preparing vaccines, in olden days,microbes were injected in the bodies of horses ormonkeys. These laboratory animals used to makeantibodies to defend these microbes. Antibodies areproteins which can act against the disease-causinggerms. These antibodies were extracted from theblood of these animals and were used as vaccines.(2) Now-a-days with the advent of biotechnology,the vaccines are manufactured in laboratories withthe help of bacteria. For this purpose, a detailedstudy of the disease causing germ is undertaken.The genes and the DNA of such microbes arethoroughly explored. Then based on thisinformation, proteins which can act against suchmicrobes are synthetically prepared in thelaboratories. The safe vaccine is produced in such away which can defend the body against infections.3) Some types of vaccines are prepared from theextracts of germs. These germs or microbes aredeactivated and made dormant. When they areinjected in the body of a person, they initiate thedefending action. The body of such vaccinatedperson, already develops the antibodies in his or herbody. When in future, this person is again attackedby similar germs the defence starts immediately andthe person does not become sick.
