small dam of height h = 1.2 m is constructed of vertical wood beams AB of thickness t = 113 mm, as shown in the figure. Consider the beams to be simply supported at the top and bottom. etermine the maximum bending stress max (in MPa) in the beams, assuming that the weight density of water is y = 9.81 kN/m³. (Enter the magnitude.) MPa

A pontoon bridge (see figure) is constructedof two longitudinal wood beams, known as balks,that span between adjacent pontoons and supportthe transverse floor beams, which are called chesses.For purposes of design, assume that a uniform floorload of 7.5 kPa acts over the chesses. (This loadincludes an allowance for the weights of the chessesand balks.) Also, assume that the chesses are 2.5 m long and that the balks are simply supported with aspan of 3.0 m. The allowable bending stress in thewood is 15 MPa.(a) If the balks have a square cross section, what istheir minimum required width bmin?(b) Repeat part (a) if the balk width is 1.5 b andthe balk depth is b; compare the cross-sectionalareas of the two designs.

A railroad tie (or sleeper) is subjected to two rail loads, each of magnitude P = 177 kN, acting as shown in the figure. L 9 £a The reaction q of the ballast is assumed to be uniformly distributed over the length of the tie, which has cross-sectional dimensions b 300 mm and h = 250 mm. Calculate the maximum bending stress o (in MPa) in the tie due to the loads P, assuming the distance L = 1,500 mm and the overhang length a = 495 mm. (Enter the magnitude.) max MPa

A horizontal beam of length 4 m and mass 9.0 kg has a mass of 3.0 kg and width 0.8 m sitting at the end of the beam (see the following figure). What is the torque due to gravity (in N m) on the beam-block system about the support at the wall? (Enter the magnitude.) Wall support 0.8 m, 3.0 kg 4 m, 9.0 kg N-m