읽고 생각하는 문제

☞10월호 문제

☞11월호 문제

읽고 생각하는 과학문제

● 11월호 문제                                                       ☞11월호 문제풀이

1. A kiloton (kt) of TNT is the energy released in the chemical explosion of 1000 kg of TNT.  A kt is equal to approximately 4x10^12 J (Joules).   Enrico Fermi famously measured the energy release of the first fission test at Trinity by dropping a steady stream of shredded bits of paper as the thermal blast wave reached the observation site 10 miles (~15 km) from the explosion.  If the paper bits were displaced a distance of 1 meter by the blast, what was the energy released in kt ?

 

A.     0.1 kt

B.       1 kt

C.     30 kt

D. 1000 kt

E. 3000 kt

 

    This event is depicted in the film "Infinity" directed by and starring Matthew Broderick.  This film is a love story and an excellent depiction of the early life of Richard Feynman.

 

 

2.  From kt to Mt ("from kilotons to megatons").  The fission blasts at Trinity, Hiroshima and Nagasaki derived their energy from the mass difference between uranium (U) or plutonium (Pu) and their fission products (typically barium and strontium).  The binding energy difference is about 1 MeV per nucleon  and U and Pu have about 240 nucleons.  (Google "binding energy curve or see Wikipedia.)

    Therefore, the energy release is about 240 MeV per fission, and since 1 MeV ~ 2x10^(-13) J, the energy release from 1 kg (~4 moles) of U or Pu is approximately 20 kt.

 

   A fusion blast derives from the mass difference of the hydrogen isotopes tritium (t) and deuterium (d) and their fusion product He-4 which is about 5 MeV per nucleon per fusion.   What is the energy release from 10 kg of a d-t mixture ?

 

A.   0.001 Mt  (1 kt)

B.    0.01 Mt

C.     0.1 Mt

D.        1 Mt

E.     100 Mt

 

 

3. The nuclear arsenal is "degrading" because tritium has a half-life of only 12.3 years.   The deuterium and tritium is stored in lithium- hydride (LiH) form as a lithium-tritide-deuteride mixture.   If a 3 Mt weapon is built, what is its approximate blast capacity after 25 years ?

 

A.        6 Mt

B.        3 Mt

C.     1.5 Mt

D.    0.75 Mt

E.    0.10 Mt

 

 

4.  Many argue that a new weapon has to be tested to ensure that it will function as expected.   The complexity of a fusion weapon has been compared to a particle accelerator such as the one at the Pohong Accelerator Laboratory (PAL), an accelerator/storage ring/beam lines complex near Daegu consisting of hundreds of precision elements that define the necessary electric and magnetic fields.  If the reliability of each of 100 components is 99.9% at any one time, what is the probability that the weapon or accelerator will function when required?

 

A. 100 %

B.   90 %

C.   50 %

D.     1 %

E.     0 %

 

 

※ 이 문제들은 미국의 SAT 문제외 비슷한 수준으로 독자 여러분의 실력 향상에 조금이나마 이바지 하고자 본사가 의뢰한 미국 전문가가 직접 출제한 것입니다. 이번 호의 정답은 다음 호에 실릴 것입니다. 풀이를(이름,생년월일,주소,전화번호 포함) 2007년 11월 30일까지 아래의 주소로 보내주십시오.

만점자가 많은 경우 추첨으로 5명을 선별하여 10만원의 장학금을 드립니다.

받는주소: 고려대학교 이과대학 물리학과 박성근 교수

              서울시 성북구 안암동5가 1번지 우:136-701

              e-mail:sungpark@korea.ac.kr