Is it possible that productivity and diversity of natural community remain constant over a time period of, say one hundred years?

There have been suggested that the value of the gravitational constant G becomes smaller when considered over very large time period (in billions of years) in the future. If that happens, for our earth.

These questions consist of two statement each, printed as Assertion and Reason. While answering these questions, you are required to choose any one of the following four responses. A. If both Assertion and Reason are true and Reason is a correct explanation of the Assertion. B. If both Assertion and Reason are true but Reason is not a correct explanation of the Assertion. C. If Assertion is true but Reason is false. D. If both Assertion and Reason are false. Assertion: Rate or extinction of wildlife has become rapid in the last one hundred years. Reason: Unplanned human activities like population explosion, deforestation, industrialization , hunting etc. have destroyed the natural habitats of many spp. of wildlife.

These questions consist of two statements each, printed as Assertion and Reason. While answering these questions,you are requied to choose any one of the following four responses If both Assertion and Reason are true and Reason is a correct explanation of the assertion If both Assertion and REason are true but Reason is not a correct explanation of the Assertion If Assertion is true but Reason is false If both Assertion and Reason is false. Assertion:Rate of extinction of wildlife has become rapid in the last one hundred years Reason: Unplanned human activities like population explosion, deforestation, industriliazation, hunting etc have destroyed the natural habitats of many spp. of wildlife.

A vibration magnetometer consists of two identical bar magnets, placed one over the other, such that they are mutually perpendicular and bisect each other. The time period of oscillation in a horizontal magnetic field is 4 second. If one of the magnets is taken away, find the period of oscillation of the other in the same field.

A country has a food deficit of 10%. Its population grows continuously at the rate of 3% per year. Its annual food production every year is 4% more than that of the last year Assuming that the average food requirement per person remains constant, prove that the country will become self-sufficient in food after n years, where n is the smallest integer bigger than or equal to (log_e 10-log_e 9)/((log_e 1.04)-0.03)

Agreat physicist of this century (RA.M. Dirac) loved playing with numerical values of Fundamental constants of nature. This led him to an interesting observation. Dirac found that from the basic constants of atomic physics (c, e, mass of electron, mass of proton) and the gravitational constant G, he could arrive at a number with the dimension of time. Further, it was a very large number, its magnitude being close to the present estimate on the age of the universe (~15 billion years) . From the table of fundamental constants in this book, try to see if you too can construct this number (or any other interesting number you can think of). If its coincidence with the age of the universe were significant, what would this imply for the constancy of fundamental constants ?

We would like to prepare a scale whose length does not change with temperature. It is proposed to prepare a unit scale of this type whose length remains, say 10 cm. We can use a bimetallic strip made of brass and iron each of different length whose length (both components) would change in such a way that difference between their lengths remains constant. If alpa_(iron = 1.2 xx 10^-5 //K and alpha_(brass = 1.8 xx 10^-5//K , what should we take as length of each strip?

classically an electron can be in any orbit around nucleus of an atom. Then what determines the typical atomic size? Why is an atom not, say, thousand times bigger than its typical size? Thequestion had greatly puzzled Bohr before he arrived at his famous model of the atom that you have learnt in the text. To simulate what he might well have done before his discovery, let us play as followswith the basic constants of nature e, me, c and see if we can get a quantity with the dimensions of length that is roughly equal to the known size of an atom (~ 10 m).- You will find that the length obtained above is many orders of magnitude smaller than the atomic dimensions. Further, it involves c. But energies of atoms are mostly in non-relativistic domain where c is not expected to play any role. This is what may have suggested Bohr to discard c and look for else h had already made its appearance elsewhere. Bohr lay in recognising that h, m_e , and e will yield the right atomic size. Construct a quantity with the dimension of length from h, me, and e and confirm that its numerical value has indeed the correct order of magnitude.

STATEMENT-1: The voltage of mercury cell remains constant for longer period of time. STATEMENT-2: It is because net cell reaction does not involve ions.

In each of the following problems, clearly state what the relevant and irrelevant factors are while going through Steps 1, 2 and 3 given in this chapter :- Suppose a company needs a computer for some period of time. The company can either hire a computer for Rs 2,000 per month or buy one for Rs 25,000. If the company has to use the computer for a long period, the company will pay such a high rent, that buying a computer will be cheaper. On the other hand, if the company has to use the computer for say, just one month, then hiring a computer will be cheaper. Find the number of months beyond which it will be cheaper to buy a computer.