Open-Ended Wrench The machinist’s wrench is being used to tighten a hexagonal nut. Calculate the moments produced by the 35-lb force about the center of the nut when the force is applied to the wrench in the orientations (a) and (b) as shown. The overall length of the handle, which is inclined slightly upward, is 6\frac{1}{4} in. long between centers of the open and closed ends. Report your answer in the dimensions of ft · lb. (See Figure 4.12 on page 144.)
Approach
We are tasked with calculating the moments in two orientations. We first assume that we can neglect the moment created by the weight of the wrench. Then we will need to use the perpendicular distances in both cases. When the force acts straight down in case (a), the perpendicular distance from the center of the nut to the force’s line of action is d = 6 in. The inclination and length of the wrench’s handle are immaterial insofar as calculating d is concerned because the handle’s length is not necessarily the same as the perpendicular lever arm’s.
