game simulation using dynamic hinges generation issue...!

Hi All,

    http://www.2dplay.com/pendulum/pendulum-play.htm  

                  Please go through the above link. I am asked to develop the same simulation in unity 3d. I've don the simulation as given below..  

1) Made a static pendulum using hinge and static joints.
2) used ray casting for the mouse click input detection.
3) made an empty object and attached hinge joint to it(at top of string). and dragged the string and bob
objects into the empty game object. tried to instantiate the empty object which is having the hinge
on top of it according to the mouse click position.
ISSUES: 1)unable to destroy the object and which is having the hinge joint. and
how to instantiate the pendulum according to the gravity and physics as same as the above
application which I attached above...!
Can u please forward me to make this simulation with clear description,
if it is possible...
Thanks a ton in advance..