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This is Giancoli Answers with Mr. Dychko. Kinetic energy is one-half mass times velocity squared and we can solve for v by multiplying both sides by 2 over m and then we take the square root of both sides and we get v. So v is the square root of 2 times kinetic energy divided by mass so that's square root of 2 times the kinetic energy of 6.21 times 10 to the minus 21 joules, for an oxygen molecule, divided by an oxygen molecule's mass of 5.31 times 10 to the negative 26 kilograms that gives us speed of about 484 meters per second.