Calculate the force exerted by the biceps to hold up the forearm and a book whose mass m = 2.6 kg. The pivot point is at the elbow joint. Weight of forearmarm is 2.5 kg. Solution: holding uprotational equilibrium Which influences tend to change the state of rotational motion? tau = F lever arm; tau counterclockuorse = tau clochutse; tau bicen 4 = tau bock + tau forearm; F bicegs *4cm=Weight book *40cm+Weight arm *15cm