You see a penny lying on the ground. A penny won't buy much these days, so you think: "If I bend down to pick it up I will do work. To do that work I will have to burn some energy. It probably costs me more to buy the fuel (food) to provide that energy than I would gain by picking up the penny. It's not cost effective." You pass it by. Required:
a. Is the argument correct?
b. Estimate the energy cost for picking up a penny.

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?