A person holds a bundle of hay over his head for 30 minutes and gets tired. Has he done some work or not? Justify your.answer.

What is the work done by the force of gravity on a satellite moving round the earth? Justify your answer.

A man walks on a straight road from his home to a market 2.5 km away with a speed of 5 km h ^-1 . Finding the market closed, he instantly turns and walks back home with a speed of 7.5 km h^-1 . What is the average speed of the man over the interval of time (i) 0 to 30 min, (ii) 0 to 50 min, (Hi) 0 to 40. min? [Note: You will appreciate from this exercise why . it is better to define average speed as total path length divided by time, and not as magnitude of average velocity. You would not like to tell the tired man on his return home that his average speed was zero!]

Science, like any knowledge, can put to good or bad use, depending on the user. Given below are some of the applications of science. Formulate your views on whether the particular applicatioa is good, bad -orsomething that cannot be so clearly, categorized : (a) Mass vaccination against small pox to curb and finally eradicate this disease from the population. (This has already been successfully done in India). Television for eradiction of illeteracy and for mass communication of news and ideas. Prenatal sex determination Computers for increase in work efficiency.. . Puttiing artificial satellites into orbits around the Earth. Development of nuclear weapons. Development of new and powerful technique of chemical and biologicaal warfaree. Purificaitoin of water for drinking. plastiic Surgery and cloning.