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# Tag Archives: wikipedia

## Nature of Electromagnetic Waves

When we represent the frequency, amplitude, and wavelength of any electromagnetic radiation on a graph we see a wave like in water. Is this just a geometric representation or do the “packet” aspects of these waves actually move physically like the mathematical representation.

Hope that the following videos explain the concept better

## Buoyancy

A pound coin floating in mercury (Photo credit: Wikipedia)

I read in one of my chapters that when a body is immersed in a container of water (kept on a weighing machine which  reads ‘W’ at first )the apparent weight lost by the body is equal to the buoyant force, and thus the reading ‘W’ increases.

Then I came across a question like this –

A beaker containing water kept on a weighing machine weighs W. A body of weight  ‘w’ is dropped in it. It is floating & experiencing a buoyant force B, then the reading on machine is –

(a)w+W
(b)W+B
(C)W+w-B
(d)W

the book says answer is (a)
but I think it is (c)

(Anwesha posted this questions)

The total force acting downwards is W+w and the weighing scale is providing an equal reaction. the normal reaction offered by the weighing scale is what we get as the reading.

therefore the reading on the weighing scale must be W+w

The buoyant force is acting on the object dropped and is not contributing to the normal reaction offered by the weighing scale.

## Speed of Light and Protons

If the definition of the speed of light is for massless particles, then how is a proton, having mass, accelerated to the speed of light?  This sounds like a conumdrum.

Posted Thierence

No massive particle has not so far crossed the speed of light. Even the extremely light particles – the neutrinos – couldnot cross the speed of light. Protons have not crossed the speed of light. When it nears the speed of light, the relativistic mechanics will become prominent and the it is to be treated is different from the classical mechanics.

## Can the process of Pair Production be used as a source for energy generation in space?

Can the process of Pair Production

be used as a source for energy generation in space?  Can Gamma Rays in space become the source for generating  energy using Pair Production process?  EM radiation >1.02 MeV enery, Pair Production is the dominant absorption process.

(Posted By Chintan Shah)

Have an answer? Post as comment now!

## Black Holes and Space

Is it possible that matter falling into a black hole would emerge in some form of elementary particles or energy in some other point in space or even time (space/time)?

I thought that matter couldn’t be destroyed just transformed into energy or some other form of matter.

Articles or theories on what happens to matter falling into a black hole say that it just falls out of existence.  That doesn’t make sense.

(Posted by Victor )

Responses:
“I have few knowledge about this subject, even though I think that ordinary matter when enters into blackholes may convert into darkmatter, ie energy associated with ordinary matter escapes & the matter will convert into darkmatter. From the origin of our universe this process may take place & this may be the reason that the amount of darkmatter is greater than that of ordinary matter.Here matter is not destroyed because total matter(including dark matter & visible matter ) remains constant.” … Anitha Anand (Student at university college,TVM)

## Problem from Kinematics

A particle moving with constant acceleration describes in the last second of its motion 9/25th of the total.if it starts from rest how long is the particle in motion and through what distance does it move if it describes 6 cm in first sec

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