You are right. Arrive at the correct answer by multiplying the wrong value by another 1.5. Comes out to 830.4 tons of TNT. Which coincides with MichaelSmith's comment: "I saw another estimate of about a 1000 which is close enough."
"A very small, few-meter sized asteroid, designated 2008 TC3..."
"It is very unlikely that
any sizable fragments will survive passage through the Earth's atmosphere..."
Let's pretend that "few-meter-sized" means 3m in diameter, that the space rock is perfectly spherical and will hit the Earth's surface in one piece.
Mass of asteroid = density*volume = (3000kg/m^3)*(4*pi*(1.5m)^2/3) = 28274.334 kg
(Density data from an eyeball-average of table in http://aa.usno.navy.mil/faq/docs/asteroid_masses)
If it hits the surface at 12800m/s, then:
Kinetic energy =.5*mv^2 = 2316233431638.683 J ~ 2316 gigajoules
1 ton TNT = 4.184GJ (from http://en.wikipedia.org/wiki/Joule), so the meteorite impact is roughly 553.6 tons of TNT.
Caveat emptor: many, many approximations.
Slashdot Mirror
You are right. Arrive at the correct answer by multiplying the wrong value by another 1.5. Comes out to 830.4 tons of TNT. Which coincides with MichaelSmith's comment: "I saw another estimate of about a 1000 which is close enough."
"A very small, few-meter sized asteroid, designated 2008 TC3..." "It is very unlikely that any sizable fragments will survive passage through the Earth's atmosphere..." Let's pretend that "few-meter-sized" means 3m in diameter, that the space rock is perfectly spherical and will hit the Earth's surface in one piece. Mass of asteroid = density*volume = (3000kg/m^3)*(4*pi*(1.5m)^2/3) = 28274.334 kg (Density data from an eyeball-average of table in http://aa.usno.navy.mil/faq/docs/asteroid_masses) If it hits the surface at 12800m/s, then: Kinetic energy = .5*mv^2 = 2316233431638.683 J ~ 2316 gigajoules
1 ton TNT = 4.184GJ (from http://en.wikipedia.org/wiki/Joule), so the meteorite impact is roughly 553.6 tons of TNT.
Caveat emptor: many, many approximations.