| |||||||
SOLUTIONS TO EXERCISE 4
SOLUTIONS TO EXERCISE 4 (a) The density of the asteroid is 7.9 g/cm^3, or 7900 kg/m^3 put into MKS units. The spherical asteroid is 10 km across, so its radius is 5 km or 5000 m. So the asteroid's mass is its density times volume: 4 * pi m = DV = 7900 kg/m^3 * ------ * (5000 m)^3 = 4.1 * 10^15 kg 3 Thus the asteroid's kinetic energy is (0.5) * mv^2, or E = (0.5) * (4.1 * 10^15 kg) * (30,000 m/s)^2 = 1.9 * 10^24 Joule. (b) What's the most destructive thing on Earth that I'm aware of? I would probably have to say an atomic bomb. I suspect that the total explosive power of all the nuclear weapons in the world could be enough to cause mass extinction. So I will compare the total energy output of these weapons with the kinetic energy carried by this meteorite. Estimates vary, but numerous sources on the WWW and elsewhere put the total amount of explosive power in nuclear weapons worldwide at about 500,000 times the power of the atomic bomb detonated over Hiroshima on August 6, 1945. That bomb had an explosive yield of about 18 kilotons of TNT; and one kiloton of TNT is equivalent to one trillion Joules (10^12 J) of energy. Thus, this asteroid carried an amount of kinetic energy roughly equivalent to 1.9 * 10^24 Joule --------------------------- = 210,000 times more energy than all the 500,000 * 18 * 10^12 Joule nuclear weapons in the world today. It's not hard to imagine that this impact could indeed have wiped out the dinosaurs. |