ARCHIMEDES' PRINCIPLE

Came across this at school, early 1950s. Funny how some things stick!

ARCHIMEDES' PRINCIPLE

Students of physics are frequently told
Of experiments performed by great physicists of old
Like Boyles and Charles - but greatest of these
Was the Principle discovered by Archimedes.

The Sicilian King, Archimedes was told,
Ordered a crown from a large lump of gold,
And though the weight of the gold was completely correct,
The goldsmith's eye made the King suspect
That he'd made up the weight with some cheaper metal
And stolen some gold, that his debts he might settle.
His problem was then of outstanding immensity
As he had no idea, whatsoever, of density.

Climbing into a bath he received a surprise
When he noticed the water beginning to rise.
He suddenly snapped, and let out a scream,
As he realized, with joy, his long-wished-for dream.

He found the upthrust, produced on a body's base*,
To be equal in weight to the water displaced,
And soon volumes and weights would make it quite plain
What various metals the crown could contain,
And so he could easily show to his Royalty
The absolute proof of the goldsmith's disloyalty.

Leaping out of the bath at remarkable rate,
He made for the palace by doorway and gate
But the men in the street were completely confounded
To see a naked man shout "Eureka! I've found it!"

* Is this the only error? The upthrust is not on the base, but at the Centre of Pressure.
By: Brian Redmile, bredmile@iafrica.com

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What Is a Black Hole, Really?

A black hole is a celestial object of such extremely intense gravity that it attracts everything near it and prevents everything, including light, from escaping. The term was first used in reference to a star in the last phases of gravitational collapse.

Gravitational collapse begins when a star has depleted its steady sources of nuclear energy and can no longer produce the expansive force, a result of normal gas pressure, that supports the star against the compressive force of its own gravitation. In some cases, nothing remains to prevent the star from collapsing without limit to an indefinitely small size and infinitely large density, to create a black hole.

At this point the effects of Einstein's general theory of relativity become paramount. According to this theory, space becomes curved in the vicinity of matter (this is the meaning of gravity); the greater the concentration of matter, the greater the curvature (the greater the gravity). When the star shrinks below a certain size determined by its mass, the extreme curvature of space seals off contact with the outside world. The place beyond which no radiation can escape even not light.

It is now believed that the origin of some black holes is nonstellar. Some astrophysicists suggest that immense volumes of interstellar matter can collect and collapse into supermassive black holes, such as are found at the center of some galaxies.

Because light and other forms of energy and matter are permanently trapped inside a black hole, it can never be observed directly. However, a black hole could be detected by the effect of its gravitational field on nearby objects (e.g., if it is orbited by a visible star), during the collapse while it was forming, or by the X rays and radio frequency signals emitted by rapidly swirling matter being pulled into the black hole. A small number of possible black holes have been detected, although none of the discoveries has been conclusive.

from http://www.juliantrubin.com/

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Physicist and Cartoon

By Salomo Simanungkalit

Presence of book Kartun Fisika, masterpiece Larry Gonick and Art Huffman, what translated to Indonesia by publisher KPG ( Popular Bibliography of Gramedia) be fresh breeze for they geting acquainted with physicist through? via mathematics as inlet. With visualisation of cartoon, physicist concepts exposed to story. Equation of continuitys of mathematics to explain the concept is started with the relation of simples with operation adds, less, times, for.

Some concepts which able to fall to become " abstraction" by teacher which is inability, at this book exposed to good. Acceleration understanding of negativity, for example. Negative acceleration concept exposed to some illustrations, partly becomes bridge to comprehend force concept.

This of course typical of way of a teacher which really learning explains one concepts with various approachs to draw up pupil comprehends other concept that tied with the concept. Art Huffman, writer of this book, of course demonstration program staff of teaching of physicist in Universitas California, Kiosk Angeles ( UCLA) is getting PhD in physicist from Universitas Washington.

Physicist with cartoon, in meaning of cartoon as instrument of visualisation assisting understanding, gets the momentum is in this book when explaining electricity phenomenon and magnetism. Differed from mechanics which able to be taught only with line sketch and point to enable pupil gets optimal understanding, electricity and magnet in class would more youngly is comprehended by means of physic. Cartoon at chapter about electricity and magnet in this book hardly assists reader to comprehend the concepts without present in physic class.

the biggest disease at schoolbook writer in school in Indonesia is disability they make story, story, when explaining physicist concepts. As of centipede story of inventor physicist figures, more than anything else pememang Nobel, deconvolution have never been found in school Iesson.

Physicist Cartoon published by the year 2001 by KPG and the British version, The Cartoon Guide to Physics, circulates strarting the year 1990 artfully inserts some stories about the role of Aristoteles, Galileo, Newton, Einstein in physicist, until physicist issues which still level of discourse like Big Bang.

" During for centuries, the physicists below shadow Aristoteles..." ( yard 18), or " having Berkat kejeniusan Galileo, we can tell not necessarily to maintain permanent substance..." ( 19), or " Setelah a few discusing, scientist finds way to express momentum property scientifically..." ( 69) at first sight impressed trivial. However, they fond of reads history of development of science will understand how storys like this very important to be introduced as information necessary for whosoever which will get acquainted with physicist in more intact.

This book consisted of two big divisions of physicist area: mechanics and electricity and magnet. Each consisted of 11 chapters and 13 chapters. Except acquaintanceship to quantum electrodynamics in last chapter, this chapter sequences of course conventional. But, presentation and way of says it is no doubt again shows how the writer and the cartoon maker understands how making physicist easier to be understood.

Chapter 12 started with, " Now we change over from mechanics to electricity and magnet. In mechanics, matter core content called as earth. In electrical science, the basis concept is cargo". Grand extraordinary opening of which only can be written a is understanding correct of the physicist and future. Earth and cargo: this is two of so much project of complete had not physicist is pared by run-out since Aristoteles " masters" physicist 2300 last year till now.

Not abundant Arno Penzias, receiver Physic Nobel the year 1978, in this book back over cited tells, " I really likes this book as entertainment amusement, at the same time discovers it is as a means of assists useful teaching. I always gives this book as signal ' thank'."

Physicist Cartoon is the correct gift for they which will complement the understanding about physicist, but also for them which swabelajar physicist will for hobby and also for a need.

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