Three identical balls are thrown from the same height off a tall building. They are all thrown with the same speed, but in different directions. Ball A is thrown in the horizontally, parallel to the roof; ball B is thrown at an angle 45° above the horizontal; ball C is thrown at an angle 45° below the horizontal. Which ball has the greatest speed just before it hits the ground? Assume that the ground near the building is level, and ignore any effects due to air resistance.

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?