[sjastro]

"impart a minimum accelerating force on that pin equivalent to the gravitational force of 4 pins."

The criteria to get a pin airborne is >1g. To suggest a juggler with an underarm action can obtain 4g is ridiculous.

This is the total force on the bridge at 4g acceleration.

1 pin= 2g, gravitational force of 4 pins= 4 X 2g.
Weight of juggler = 47 kg. (Should have included this in my last post).

Weigth of Juggler + reaction force on bridge = 47 kgf + 4 X 2g = 125.4 kgf.

Total force = 125.4kgf

According to you the answer should be 57 kgf.
As Paul enquired show us how you obtained this result

This is my final contribution in this thread.

Regards

Steven