Suppose the Sun's gravity were turned off, and the planets would leave their nearly circular orbits and fly away in straight lines described by Newton's first law. Would Mercury ever be farther away from the Sun than Pluto? If so, how long would it take for Mercury to acheive this passage? I know this problems must have something to do with Kepler's laws, b/c its out of that section of the book. But I'm guessing you would have to find the tangential velocity first, or at some point?