An astronaut inside a small space ship orbiting around the earth cannot detect gravity. If the space-station orbiting around the earth has a large size, can he hope to detect gravity?

Suppose there existed a planet that went around the sun twice as fast as the earth.What would be its orbital size as compared to that of the earth?

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.

A LASER is a source- of very intense, monochromatic, and unidirectional beam of light. These properties of a laser light can be exploited to measure long distances. The distance of the Moon from the Earth has been already determined very precisely using a laser as a source 'of light. A laser light beamed at the Moon takes 2.56 s to return after reflection at the Moon’s surface. How much is the radius of the lunar orbit around the Earth?