69. Each side of the trough exerts a normal force on the crate. The first diagram shows the view looking in toward a cross section. The net force is along the dashed line. Since each of the normal forces makes an angle of 45° with the dashed line, the magnitude of the resultant normal force is given by 2cos452NrNNFFF=°=.The second diagram is the free-body diagram for the crate (from a “side” view, similar to that shown in the first picture in Fig. 6-53). The force of gravity has magnitude mg,wheremis the mass of the crate, and the magnitude of the force of friction is denoted by
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