For a given level of technology, there is a maximum density of "bits" of information that can be stored on a computer's hard-drive disk. the data are stored in a tight spiral, so that "tracks" are essentially circles of increasing radius from inner to outer parts of the disk. as the disk spins at a constant rate, data are read at a constant rate regardless of the radius of the track being read.

An alpha particle with kinetic energy 12.5 mev makes a collision with lead nucleus, but it is not "aimed" at the center of the lead nucleus, and has an initial nonzero angular momentum (with respect to the stationary lead nucleus) of magnitude l = p0 b, where p0 is the magnitude of the initial momentum of the alpha particle and b=1.40×10−12 m. (assume that the lead nucleus remains stationary and that it may be treated as a point charge. the atomic number of lead is 82. the alpha particle is a helium nucleus, with atomic number 2.) what is the distance of closest approach?