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 Subject: nuclear physics Category: Science > Physics Asked by: travis18-ga List Price: \$15.00 Posted: 20 Apr 2005 10:48 PDT Expires: 20 May 2005 10:48 PDT Question ID: 511836
 ```How can I convert the kinetic energy of an incoming meteroid to equivalent Atomic Bomb or Hydrogen Bomb blast? Basically, I want to know How much energy is produced by an Atomic or Hydrogen bomb in Joules.```
 Subject: Re: nuclear physics Answered By: welte-ga on 20 Apr 2005 16:23 PDT Rated:
 ```Dear Travis, Thank you for question on meteors and atomic bombs. The kinetic energy in the meteor can be expressed as: K = ½ mv^2 However, as the object hurtles toward the Earth, it gains kinetic energy as its potential energy is converted to kinetic. Therefore, one must consider the total energy in the object: E = ½ mv^2 + mgh Just before impact, the height will decrease to zero (at impact) and all of the energy will be kinetic energy. For simplicity, I will neglect loss of energy to resistance due to the atmosphere and effects of heating secondary to friction with the atmosphere during descent. Of course, if one could measure the velocity of the object just prior to impact, these effects would be inherently be taken into account (the friction has already had its effect at that point), so one can either calculate the equivalent energy based on the energy of the object at a height above the impact site, or one can calculate the equivalent energy more accurately by measuring the instantaneous velocity (and mass) must prior to impact. The math is essentially the same. So, the total energy is given above, and is constant (conservation of energy). With the units below, the energy calculated will be in Joules. To convert to "atomic bomb units," also known as "equivalent tons of TNT", we use the conversion 1 megaton (1 million metric tons) of TNT = 4.185 x 10^22 ergs = 4.185 x 10^15 Joules or, one can say, there are 2.39 x 10^-16 megatons per Joule A very complete physics unit conversion document can be found here: http://scholar.google.com/url?sa=U&q=http://www.agu.org/reference/gephys/23_moskowitz.pdf Table 4 on page 5 of the above document give multiple energy unit conversions. The answer, then, is a matter of substitution of the conversion factor into the energy equation: Energy (in megatons TNT) = E * megatons / Joule = E * ( 2.39 x 10^-16 megatons / Joule) = (½ mv^2 + mgh) * ( 2.39 x 10^-16 megatons / Joule) An *excellent* resource for both derivations and discussion of the many ramifications of such an impact is the following article: "Comet and Asteroid Threat Impact Analysis," by James A. Marusek. http://scholar.google.com/url?sa=U&q=http://personals.galaxyinternet.net/tunga/TA.pdf This document includes multiple estimates on the many variables involved (e.g., object density, velocity, etc.) Another good article can be found here: http://scholar.google.com/url?sa=U&q=http://www.geocities.com/elidoro/collaborazione/whitepaper.pdf ____________________________________________________ Here are definitions of all of the variables I've used above with the units in brackets: K: Kinetic energy [joules] m: mass of object [kilograms] v: velocity of object [meters/second] E: Total energy of object [joules] g: gravitational acceleration constant (9.8 m/s^2) h: height of object from impact site [meters] ____________________________________________________ I hope this was helpful. Feel free to request clarification. Best, -welte-ga```
 travis18-ga rated this answer: `exactly what I needed. great answer and very fast`

 ```From: http://online.unitconverterpro.com/conversion-tables/convert-group/energy.html and http://www.onlineconversion.com/energy.htm 1 gigajoule = 2.3900573613767E-007 megatons or in easier form for your purposes, 1 megaton = 4,184,000 gigajoules. (add another 9 zeros for just joules) From http://www.cnn.com/SPECIALS/cold.war/experience/the.bomb/history.science/ The two bombs dropped during WW2 were 15kilotons = 6.276 * 10^13 joules and 60 kilotons = 2.51*10^14 joules```
 ```You might also find the following on-line resources interesting/useful: uses scaling relations "to determine the diameter of a crater given details on the nature of the projectile, conditions of impact, and state of the target". and which estimates "the regional environmental consequences of an impact on Earth. This program will estimate the ejecta distribution, ground shaking, atmospheric blast wave, and thermal effects of an impact as well as the size of the crater produced. " This calculator will also tell you the both the total kinetic energy (in MT) of a impacting object as well as the energy deposited during the impact (they are not the same).```