즐거운 인생, 즐거운 물리

벤츠의 스마트와 S클래스의 충돌 영상이다.

S클래스의 질량은 2308kg 스마트는 1124kg 으로 질량비율은 2.05 : 1 이다.

충돌 영상 중 파란색으로 표시되는 탑승 영역이 안전하게 보호되는 모습을 강조하였다.

'작은 차도 안전하게만 만들면 되겠구나' 라는 인식을 가지기에 충분해 보인다.

하지만 위 광고에서는 충돌 직후의 모습을 보여주지 않는다.

S클래스보다 작은 C클래스와 스마트의 충돌영상이다.

운동량 보존법칙에 의해서 충돌할 때 두 자동차의 운동량의 변화량은 같다. 따라서 속도의 변화량 (가속도)은 상대방의 차와 내 차의 질량에 비율에 따라 결정된다.  

영상의 C클래스는 1590kg 스마트는 820kg 으로 질량비율은 1.93 : 1 이다. 충돌 시 탑승자의 가속도(알짜힘)는 2배가량 차이가 나게 된다. 충격을 2배만큼 더 받게 되어 내부 공간은 보호 될지라도 내부에서 받는 충격은 2배가 된다.

질량 비율을 비교해 보면 두 차가 충돌했을 탑승자가 받는 충격을 대략 비교해 볼 수 있다.

내차는 모닝이니까 아내차인 아반떼와 충돌하면 아반떼보다 1.33배의 충격을 받는다고 볼 수 있다. 요즘 차량 사고에 걱정이 많아져서 싼타페로 바꾼다면 모닝과 충돌시 모닝 탑승자에 비해 절반정도 충격을 받는다. 대한민국 사람들이 보여지는것에 민감하여 큰차를 산다고 하지만 위와같은 물리학적인 요소가 포함되는것이다. 대형버스와 충돌한다면 모닝이든 싼타페든 같다고 하지만 그나마 싼타페가 좀 더 낫다. (모닝 15.8, 싼타페 8.1)

After 350 Years, Vatican Says Galileo Was Right: It Moves

By ALAN COWELL,
Published: October 31, 1992
More than 350 years after the Roman Catholic Church condemned Galileo, Pope John Paul II is poised to rectify one of the Church's most infamous wrongs -- the persecution of the Italian astronomer and physicist for proving the Earth moves around the Sun.

With a formal statement at the Pontifical Academy of Sciences on Saturday, Vatican officials said the Pope will formally close a 13-year investigation into the Church's condemnation of Galileo in 1633. The condemnation, which forced the astronomer and physicist to recant his discoveries, led to Galileo's house arrest for eight years before his death in 1642 at the age of 77.

The dispute between the Church and Galileo has long stood as one of history's great emblems of conflict between reason and dogma, science and faith. The Vatican's formal acknowledgement of an error, moreover, is a rarity in an institution built over centuries on the belief that the Church is the final arbiter in matters of faith.

At the time of his condemnation, Galileo had won fame and the patronage of leading Italian powers like the Medicis and Barberinis for discoveries he had made with the astronomical telescope he had built. But when his observations led him to proof of the Copernican theory of the solar system, in which the sun and not the earth is the center, and which the Church regarded as heresy, Galileo was summoned to Rome by the Inquisition. Forced to Recant

By the end of his trial, Galileo was forced to recant his own scientific findings as "abjured, cursed and detested," a renunciation that caused him great personal anguish but which saved him from being burned at the stake.

Since then, the Church has taken various steps to reverse its opposition to Galileo's conclusions. In 1757, Galileo's "Dialogue Concerning the Two Chief World Systems" was removed from the Index, a former list of publications banned by the Church. When the latest investigation, conducted by a panel of scientists, theologians and historians, made a preliminary report in 1984, it said that Galileo had been wrongfully condemned. More recently, Pope John Paul II himself has said that the scientist was "imprudently opposed."

"We today know that Galileo was right in adopting the Copernican astronomical theory," Paul Cardinal Poupard, the head of the current investigation, said in an interview published this week.

This theory had been presented in a book published in 1543 by the Polish scientist Nicolaus Copernicus in opposition to the prevailing theory, advanced by the second-century astronomer Ptolemy, that the Sun and the rest of the cosmos orbited the Earth. But the contest between the two models was purely on theoretic and theological grounds until Galileo made the first observations of the four largest moons of Jupiter, exploding the Ptolemaic notion that all heavenly bodies must orbit the Earth.

In 1616, the Copernican view was declared heretical because it refuted a strict biblical interpreation of the Creation that "God fixed the Earth upon its foundation, not to be moved forever." But Galileo obtained the permission of Pope Urban VIII, a Barberini and a friend, to continue research into both the Ptolemaic and the Copernican views of the world, provided that his findings drew no definitive conclusions and acknowledged divine omnipotence.

But when, in 1632, Galileo published his findings in "Dialogue Concerning the Two Chief World Systems," the work was a compelling endorsement of the Copernican system.

Summoned to Rome for trial by the Inquisition one year later, Galileo defended himself by saying that scientific research and the Christian faith were not mutually exclusive and that study of the natural world would promote understanding and interpretation of the scriptures. But his views were judged "false and erroneous." Aging, ailing and threatened with torture by the Inquisition, Galileo recanted on April 30, 1633.

Because of his advanced years, he was permitted house arrest in Siena. Legend has it that as Galileo rose from kneeling before his inquisitors, he murmured, "e pur, si muove" -- "even so, it does move."