a. A rod of length l is made of explosive material. The detonation velocity (the rate of involvement in the explosion of new parts of the explosive) is equal to v, and the rate of spreading of the products of the explosion is u < v. How does the region occupied by the products of the explosion change with time if the rod is detonated at one end? Make a drawing.
b. From the same explosive material it is necessary to make such a thin-walled conical shell so that when detonating it from the top, the products of the explosion simultaneously hit the rod on the axis of the cone. What angle between the axis of the cone and the generatrix should be chosen?