Arelatively small impact crater 20 kilometers in diameter could be made by a comet 2 kilometers in diameter traveling at 25 km/s (2.5×104 m/s ).

a) assume that the comet has a total mass of 4.2×1012 kilograms. what is its total kinetic energy? (hint: the kinetic energy is equal to 12mv2, where m is the comet's mass and v is its speed. if you use mass in kilograms and velocity in m/s, the answer for kinetic energy will have units of joules.) express your answer using two significant figures.

b)convert your answer from part a to an equivalent in megatons of tnt, the unit used for nuclear bombs. comment on the degree of devastation the impact of such a comet could cause if it struck a populated region on earth. (hint: one megaton of tnt releases 4.2×1015 joules of energy.) express your answer using two significant figures.