So how to calculate the distance between hammer and pointer on the stick (O) for our hand is not feel pain? It mean the force reaction at the point (O) should be zero. We should learn dynamic theory especially about inertia force.
The force F having moment M = F.(a+c) about O produces angular acceleration but at no angular velocity. If the applied force F is collinier with the resultant inertia force, the system is equilibrium without need horizontal reaction (Xo) at O. Hence the force of F shoul be applied a long line passing trough the center of hammer (P), that is a = ic^2/c. ic^2 is gyration radius.
Result calculation with assumtion value of force and weight of the hammer found C=1m. It is difficult to application. This formula is suitable for impact test machine.
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