How does mass depend on speed?

In order to answer this question, we have to consider two situations:

a) The object could be at rest in our reference frame.

b) The "object" is never at rest in any (physically realizable) frame of reference.

An electron and a tennis ball belong to situation (a), where as a photon belongs to situation (b)

Let us assume that two masses exist, the mass when object has zero speed 'm0' and mass 'm' when object has speed 'V' as observed in our frame of reference.

When the object has zero speed, it is at rest (as observed by us or by someone accompanying the object), and so 'm0' is called the object's rest mass. It is an intrinsic property of the object.

For instance every electron has rest mass m0=9.11 x 10^-31 Kg.

If we set into motion a tennis ball that is initially at rest, the ball acquires kinetic energy, the energy associated with motion.Its energy increases.

From the equation  E=mC2; it implies that increase in energy will correspond to increase in mass too. We deduce that ball's inertia increases. Thus the mass 'm' of moving ball is greater than the rest mass 'm0'. Hence m>m0 holds for any object with kinetic energy.

In 1905, Einstein summarized his theoretical discovery with sentence,

" The mass (i.e. the inertia) of a body is a measure of its energy content.  

 

What is wave motion?

Wave motion, in general refers to transfer of energy from one point to other point of medium.

For transfer of energy through a medium, the medium must possess the properties of
i) Elasticity ii) Inertia & iii) Negligible frictional resistance

and now the question is what propagates in wave motion?

It is not the matter that is propagated but it is only state of motion of matter that is propagated.
It may be said that in wave motion momentum and energy are transferred or propagated.

What is grounding?

Grounding is one of primary ways to minimize unwanted noise and pickup.

There are two basic objectives involved in designing good grounding systems.

i) To minimize noise voltage generated by currents from two or more circuits flowing thorugh a common ground impedance.

ii) To avoid creating ground loops which are susceptible to magnetic fields and differences in ground potential.

Grounding, if done improperly however, can become a primary means of noise coupling.

In most general sense a ground can be defined as equipotential point or plane which serves as a reference voltage for a circuit or system. By equipotential point we mean the point where voltage does not change regardless of the amount of current supplied to it or drawn from it. 

If the ground is connected to earth through a low impedance path, it can then be called an earth ground.

There are two common reasons for grounding a circuit:

i) For safety

ii) To provide an equipotential reference for signal voltages

Safety grounds are always at earth potential where as signal grounds are usually but not necessarily at earth potential.

In many cases, a safety ground is required at a point which is unsuitable for a signal ground, and this may complicate noise problem. 

  

Discovery of X-rays

Wilhelm Roentgen was professor of physics at university of Wurzburg, Germany when he discovered X-rays in 1985. The discovery was entirely serendipitous; Roentgen was merely studying a beam of electrons in a highly evacuated glass vessel. When the electrons, moving at great speed slammed into glass wall, they produced a very high penetrating radiation - a wholly unexpected occurrence. Roentgen first noticed the radiation when it caused a paper coated with Barium Platino-cyanide to glow. The chemical compound was a standard detector of UV light which causes the chemical to fluorescence i.e. to emit visible light after it has absorbed UV light. But Roentgen's evacuated vessel was tightly covered with black cardboard and so no UV light could emerge from it. The glow must be some other kind of radiation.

When he announced the discovery of the new radiation, Roentgen wrote:

"I posesss, for instance, photographs of ............the shadow of bones of hand, the shadow of a covered wire enclosed in a box.........."

Earlier in the paper, he noted that "the darker shadow of bones is seen with in the slightly dark shadow image of hand itself.

The new radiation quickly became a diagnostic tool in hospitals all over the world. Roentgen could not determine what the rays are made of and thus rays are named as X-rays.       

How is Neutron discovered?

In 1930, Bothe & Becker bombarded Lithium, Beryllium and Boron with alpha particles from Polonium and found a very penetrating but non-ionizing radiation, they assumed that the radaition was of gamma rays type because of its high penetration.

While repeating these experiments in 1932, Dr. F. Joliot and his wife, Dr. Irene Curie Joliot found that when a sheet of Hydrogen containing material, particularly paraffin, was interposed in the path of these radiations, Protons were ejected with a considerable velocity.

From the ranges of these recoil protons, the maximum proton energy 'E' proved to be about 5.3 MeV. Assuming that the protons were produced as the result of elastic collisions with the gamma ray photons, calculations showed that each photon must have possessed an amount of energy about 52MeV. These results were entirely inconsistent with the results from experiments on absorption of these in lead(about 7 MeV).

Chadwick, in England in 1932, after performing a series of measurements of energies of recoil of Protons ejected from thin targets by the penetrating "Be-radiation", with a pulse ionizing chamber and amplifier. He said, "these results are very difficult to explain on the assumption that the radiation from Beryllium is a quantum radiation, if energy and momentum are to be conserved in the collisions. These difficulties disappear, however, if it be assumed that the radiation consists of particles of mass 1 and charge 0 later named as Neutrons.          

These neutrons were formed as a result of highly exoergic nuclear reactions.

Three stage Indian Nuclear program

The three stages of Indian Nuclear Program

STAGE-1:

Construction of pressurised heavy water reactors. These reactors use natural Uranium. Spent fuel from these reactors is reprocessed to obtain Plutonium.

STAGE-II:

Construction of fast breeder reactors fuelled by Plutonium produced in stage-I. These reactors would also breed U-233 from Thorium.

STAGE-III:

Construction of power reactors using U-233/Thorium as fuel.

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