Keshav Jain

Earth rotates from west to east causing the Sun, the Moon, stars andother planets rise from

east and set in the west. On the surface of the eartheach point is moving eastward with

respect to an astronaut in space.

Thus if a rocket is launched at a small angle eastward vertically the speed of earth gets added to

the rocket’s speed. This reduces the amount of fuelrequired. If the rocket is inclined along any

other direction, the speed of the earth gets subtracted from the speed of rocket and will

necessitate burning of more fuel.

In addition, in case of any failure during launch the rocket will fall back to the earth.

Hence if it is launched from the east coast, the rocket will fall into the sea only. If it is launched from the west coast, in case of failure, the rocket will fall on the land endangering human habitats. Thus choosing eastward inclination is scientific but choice of eastern coast concerns safety.

In normal telephone exchange systems, a pair of wires extends each telephone instrument to the telephone exchange.

Normally, copper conductors are used to give loop to indicate the exchange that the 

Continue reading “How does a cell phone work?”

Down to milligrams one can use well-designed physical balances-indeed one can even o below one milligram if proper isolation from vibrations and other disturbances is ensured. But for going lower one needs to use other methods. We have to remember that our objective is to measure the mass, which is the quantity of material and not the amount of gravitational force. Mass is a measure of inertia.

Continue reading “How are minute quantities (like milligrams, micrograms, or nanograms) weighed?”

It is true that the moon makes one rotation around the earth in 27.3 days. A lunar month is the number of days between two new moon days. After one new moon day the moon does arrive at the same position with respect to the fixed stars after 27.3 days.

But it is not aligned with the earth and the sun because during this period the earth has moved some distance around the sun, indeed by about 270. So the moon has to move some more to come to a position between the sun and the earth.
A simple calculation shows that this additional traverse would take about 2.2 days. Therefore the next new moon comes after 29.5 days and not 27.3-the lunar month is longer than the period of rotation of the moon by about Two days!

The source of the smell is most probably caused by bacteria and fungi feeding on organic matter in the rubbish. It will be more noticeable if the bin is in a warm and damp place.
Continue reading “Why is that, whatever they contain, dustbins always smell the same?”

Answer 1.
Ordinary tyres or cross-ply tyres are the oldest type of tyre and has a case made of two or more layers of fabric. A tyre’s strength and load carrying ability were at one time indicated by its number of plies. Modern materials and man made fibers such as polyester and glass fiber embedded in the rubber are much stronger than the cotton fibers originally used.
Continue reading “What is the difference between radial and ordinary tyres?”

The Babylonians 3000 years ago used the hexadecimal system of numbering, which was based upon a multiplication of 6, instead of the decimal system which we now used. They divided the circle for example into 60×6 parts- the 360 degrees. Each degree in turn was divided into 60 parts was again divided into 60.
Continue reading “Why are a circle divided into 360 degrees?”

Particles of sand, sometimes sorted by water transport into deposits of remarkably uniform size, are continuously being formed, often from the bedrock of earth, by weathering and erosion by chemical and physical forces. Continue reading “Where does sand come from? Has any thought been given to manufacturing it?”

The Euro norms are meant for regulating vehicular emission in Europe. The norms are expressed in terms of the weight of pollutants such as carbon monoxide (CO), hydrocarbon (HC), oxides of nitrogen (NOx) and particulate matter emitted per kilometer of vehicular run with load. These ceilings have been fixed for various categories of vehicles. For instance, there are emission levels for petrol – driven and diesel – driven vehicles based on the capacity of the engines. The pollution measurements under engine idling conditions without application of lord on the vehicles does not reflect the exact quantum of various pollution emitted by the engines in reality.
In any internal combustion engines, as the speed or acceleration is increased, the time allowed for combustion of the fuel is varied than the idling condition. This variation is different in a carburetor engine and in a fuel injection petrol or diesel engine. In a carburetor engine, the CO will be maximum at idling speed. In a diesel engine, the smoke will be maximum upon sudden acceleration. The Euro norms adopt certain specified driving cycles related with time Vs speed. During these cycles of operation of the engine, the mass of each exhaust gas component is evaluated. The mass is computed from the measured concentrations of each pollutant in the known exhaust gas volume. Exhaust gas is generated when the vehicle is operated on a chassis dynamometer according to certain standard driving cycles which simulate driving conditions in urban traffic.

Most of us don’t think about how our everyday activities might influence the global environment. An example is our use of chlorofluorocarbons or CFCs. These compounds which are useful as propellants in aerosol sprays, refrigerants, and coolants, cleaning agents, insult ants and plastic foam are the main Easters of ozone present in the ozonosphere. Ozonosphere is the general stratum of the upper atmosphere in which there is an appreciable ozone concentration and in which ozone plays an important part in the radiative balance of the atmosphere.
It lies roughly between 10 and 50 kilometers, with maximum ozone concentration at about 20 to 25 kilometers. Ozone, O3, a blue gas is unstable allotropic form of oxygen. It is scarce, even in the stratosphere (12 – 50 km from earth’s surface) where it is most concentrated. But each molecule counts. Highly unstable, an ozone molecule readily splits up when hit by ultraviolet radiation. The energy of the life-damaging UV rays is thus converted into harmless heat and never reaches the earth. The breakup leaves a free oxygen atom (O) and an oxygen molecule (O2), the stuff we breathe. The O and O2, in an ongoing cycle, recombine to form new ozone molecules.
The chlorofluorocarbons (trade named freons) released by us are stable and can live up to 100 years.
They are non-toxic and harmless to life. But when they drift slowly upward to reach the stratosphere by convection, they are struck by the high energy short wavelength radiations such as ultraviolet rays and this initiates a ozone clearing process. When a CFC molecule is exposed to strong UV radiation in the stratosphere, it is broken apart.
This release a chlorine atom, which attacks an ozone molecule, pulls away one of the three oxygen atoms and forms a chlorine monoxide molecule thus destroying the ozone molecule. The destructive process continues further.
The oxygen atoms from the new chlorine monoxide molecule are pulled away by free oxygen atoms freeing the chlorine atom to restart the cycle: thus progressively more ozone molecules are decomposed. It has been estimated that one chlorine atom can eat up to 1,00,000 molecules of ozone. A severe depletion in the ozone layer will result in an increase in the case of skin cancer, eye cataract and suppression of the immune system in humans and other species. Food crops sensitive to UV rays could also be affected.
In 1984 a hole in the ozone layer was discovered over Antarctica and more recently a similar hole was discovered which extends over the Arctic, Scandinavia and North America.