Large ships often have circular structures in their windshields. What is their purpose? Called clearview screens, they consist of a glass
disk that is rotated at high speed by a motor in the center of the
circle) to disperse rain and spray. If the screen has a diameter of
0.40 m and rotates at 1900 rpm, the speed at the rim of the screen
is 40 m/s.

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?