For 3) and 4) that's what I noticed:
We are in an awkward situation here,
because precizamos have a minimum knowledge of algebra,
or trigonometry and analytic geometry to solve this,
once to stop the moving object
is impossible with bullets, I believe that once triggered it traverses
in one direction to be destroyed, but if we know the equation
vector of straight or director of the movement direction can be calculated
the position of the object or even the distance that must be stopped, and then
after a while the return movement.