Please folks this is simple year 11 or 12 physics. The juggler as a time average weighs 47 + 10 kg. Those pins dont hover by themselves.
Remember F delta t and change in momentum.
See here for the theory! It even goes into Relativity.
http://en.wikipedia.org/wiki/Newton's_laws_of_motion
If I was the teacher I would explain it as gravitational potential energy being equivalent to the kinetic energy of the pin depending on how far it was thrown up! The impulse needed F delta t gives you the change in momentum and hence the energy and then you can calculate a time averaged force. As a time average the juggler weighs his 47kg + 10kg of pins.
Bert