question_answer 7)

Two particles, each of mass m and speed v, travel in opposite directions along parallel lines separated by a distance d. Show that the vector angular momentum of the two particle system is the same whatever be the point about which the angular momentum is taken. 

Answer:

As shown in Fig. 7.99, suppose the two particles move parallel to the y-axis.   Fig. 7.99 Total angular momentum of the two particle system about O is                                 Clearly, I does not depend on x and hence on the origin O. Thus the angular momentum of the two particle system is same whatever be point about which the angular momentum is taken.