墜俄隕星的爆炸威力有多大 ?
本帖最後由 mca 於 2013-2-27 08:58 編輯http://forum.hkas.org.hk/Web/Meteor_Explosion_Russia_2013Feb15.jpg
http://forum.hkas.org.hk/Web/Meteor_Explosion_Russia_2013Feb15_2.jpg
2013 年 2 月中，網上消息報導 (http://spaceweather.com/)：
On Friday, February 15th at 9:30 am local time in Russia, a small asteroid struck the atmosphere over the city of Chelyabinsk and exploded. According to reports from news organizations and Russian authorities, as many as 1000 people received minor injuries from the shock wave. This is the most energetic recorded meteor strike since the Tunguska impact of 1908.
Researchers have conducted a preliminary analysis of the event. "Here is what we know so far," says Bill Cooke, head of NASA's Meteoroid Environment Office. "The asteroid was about 15 meters in diameter and weighed approximately 7000 metric tons. It struck Earth's atmosphere at 40,000 mph (18 km/s) and broke apart about 12 to 15 miles (20 to 25 km) above Earth's surface. The energy of the resulting explosion was in the vicinity of 300 kilotons of TNT."
我們不妨估計這顆隕星在爆炸時釋放的能量。
隕星的直徑 = 15 米 = 1500 cm
隕星的體積 = 4/3 (pi) (R^3) =4/3 (pi) (1500 / 2)^3 = 1.767 x 10^9 cc
設隕星的密度 = 4 g / cc
隕星的質量 = 體積 x 密度 = 7 x 10^9 g = 7 x 10^6 kg = 7000 公噸
隕星爆炸時釋放的能量
= 隕星的動能 = 1 / 2 x 質量 x 速度的平方
= (1 / 2) (7 x 10^6)(18000)^2
= 11.34 x 10^14 joules
(300,000 公噸 TNT 炸藥)
這次爆炸相當於 30 萬公噸 TNT 炸藥或 15 倍日本長崎原子彈的能量，可幸隕星在二十多公里的高空爆炸，其震波只傷及千人，假如隕星直擊地面，其威力足把一座城市催毀。
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後記：
根據事後更多監察站的音爆記錄，NASA 修正墜俄隕星的威力相當於50 萬公噸 TNT 炸藥，
參考http://www.nasa.gov/mission_pages/asteroids/news/asteroid20130215.html
Intrasound of the Meteor
http://science.nasa.gov/science-news/science-at-nasa/2013/26feb_russianmeteor/
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