Chapter 6, Problem 56IF

Impact Energy. Consider a comet about 2 kilometers across with a mass of 4 × 10¹² kg. Assume that it crashes into Earth at a speed of 30,000 meters per second (about 67,000 miles per hour).

1. a. What is the total energy of the impact, in joules? (Hint: The “kinetic energy” formula tells us that the impact energy in joules will be $\frac{1}{2}\times m\times v^2$, where m is the comet’s mass in kilograms and v is its speed in meters per second.)
2. b. A 1-megaton nuclear explosion releases about 4 × 10¹⁵ joules of energy. How many such nuclear bombs would it take to release as much energy as the comet impact?
3. c. Based on your answers, comment on the degree of devastation the comet might cause.