In 2003, the “Dinosaur Killer” asteroid crater was imaged for the first time (see National Geographic News, March 7, 2003). The crater is believed to be 100 km in radius and 1 km deep. What was the kinetic energy of the asteroid that made that crater? Express your answer in joules and in megatons (1 MT = 4 · 10 J).

How much total time is spent listening to graduation speeches in the U.S. each year?

Question suggestions are always welcome!

Look for the answers online at tpt.aapt.org under “Browse,” at the very end of the current issue.

For more Fermi questions and answers, see Guesstimation 2.0: Solving Today’s Problems on the Back of a Napkin, by Lawrence Weinstein (Princeton University Press, 2012).

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