Two friends push with great force against a rock. The forces are equally strong but in opposite directions. A heavy box rests on top of the rock. Answer these questions about the motion of the
rock Assume that the rock is light enough for either friend to carry.
One friend steps away from the rock. Does the rock move? If so, in which directions does it move. Explain

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?