Figure shows the cross section of a road cut into the side of a mountain. The solid line AA' represents a weak bedding plane along which sliding is possible. The block B directly above the highway is separated from uphill rock by a large crack (called a joint), so that only the force of friction be- tween the block and the likely surface of failure prevent sliding. The mass of the block is 1.8 X 10 7 kg, the dip angle of the failure plane is 24° , and the coefficient of static friction between block and plane is 0.63. (a) Show that the block will not slide, (b) Water seeps into the joint, exerting a hydrostatic force F parallel to the incline on the block. What minimum value of F will trigger a slide?
							
Figure shows the cross section of a road cut into the side of a mountain. The solid line AA' represents a weak bedding plane along which sliding is possible. The block B directly above the highway is separated from uphill rock by a large crack (called a joint), so that only the force of friction be- tween the block and the likely surface of failure prevent sliding. The mass of the block is 1.8 X 107 kg, the dip angle of the failure plane is 24° , and the coefficient of static friction between block and plane is 0.63. (a) Show that the block will not slide, (b) Water seeps into the joint, exerting a hydrostatic force F parallel to the incline on the block. What minimum value of F will trigger a slide?