7.1 On August 10, 1972, a large meteorite skipped across the atmosphere above the western United States and western Canada, much like a stone skipped across water. The accompanying fireball was so bright that it could be seen in the daytime sky and was brighter than the usual meteorite trail. The meteorite’s mass was about4x106kg ; its speed was about 15 km/s. Had it entered the atmosphere vertically, it would have hit Earth’s surface with about the same speed. (a) Calculate the meteorite’s loss of kinetic energy (in joules) that would have been associated with the vertical impact. (b) Express the energy as a multiple of the explosive energy of 1 megaton of TNT, which is 4.2x1015J. (c) The energy associated with the atomic bomb explosion over Hiroshima was equivalent to 13 kilotons of TNT. To how many Hiroshima bombs would the meteorite impact have been equivalent? 26214fi11mKKK0Jmv(4.0x10 kg)(15000)4.5x10J22sΔ=−=−= −= −a)b)14151megaton TNTK( 4.5x10J)0.107 megaton TNT4.2x10JΔ= −= −c)1Hiroshima bomb0.107megaton TNT107 kiloton TNT8.24 Hiroshima bomb13 kiloton TNT⎛⎞==⎜⎟⎝⎠(the problem asks for the energy as a multiple of the explosive energy which is really a dimensionless quantity)(negative sign expresses lossof kinetic energy)
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