Question
The Moon’s craters are remnants of meteorite collisions. Suppose a fairly large asteroid that has a mass of $5.00 \times 10^{12}\textrm{ kg}$ (about a kilometer across) strikes the Moon at a speed of 15.0 km/s. (a) At what speed does the Moon recoil after the perfectly inelastic collision (the mass of the Moon is $7.36\times 10^{22}\textrm{ kg}$ ) ? (b) How much kinetic energy is lost in the collision? Such an event may have been observed by medieval English monks who reported observing a red glow and subsequent haze about the Moon. (c) In October 2009, NASA crashed a rocket into the Moon, and analyzed the plume produced by the impact. (Significant amounts of water were detected.) Answer part (a) and (b) for this real-life experiment. The mass of the rocket was 2000 kg and its speed upon impact was 9000 km/h. How does the plume produced alter these results?
1. $1.02\times 10^{-6}\textrm{ m/s}$
2. $5.63\times 10^{20}\textrm{ J}$ of kinetic energy was lost.
3. $6.79\times 10^{-17}\textrm{ m/s}$, 6.25 GJ of kinetic energy was lost.
Solution Video

# OpenStax College Physics Solution, Chapter 8, Problem 40 (Problems & Exercises) (3:53)    