Calculate the shear force acting on the lumbar vertebra. calculate the compressive force acting on the lumbar vertebra The GRF is 225 N. The GRF has a moment arm of 0.40 m relative to the vertebra axis of rotation. The weight of the trunk is 350 N. Wtrunk has a moment arm of 0.3 m relative to the vertebra axis of rotation. Fm is 300 N. Fm has a moment arm of 0.05 m relative to the vertebra axis of rotation.?