Biomechanics Question

(5 marks). A construction worker must hold a sign (asking drivers to either SLOW or STOP). The sign weighs 10kg and the worker holds it with one hand, his arm stretched out 90 degrees from the axis of his body (that is, parallel to the ground). Calculate the reaction force and moment at his shoulder. Assume an arm length of 50cm from the application of the load to the shoulder. Assume his arm weight is 30N.