A boy of mass 45 kg and his dog of mass 25 kg stand on a diving board. If the boy stands 2.0 meters from the pivot of the
board, and the dog stands 1.2 meters from the pivot, what is
the net torque on the board? Use g = 9.8 m/s2

Asolid round steel rod 6.25 mm in diameter and 375 mm long is rigidly bonded to the end of solid square brass rod 25 mm on a side and 300 mm long. the geometric axes of the bare are along the same line. an axial tensile force of 5.4 kn is applied at the extreme ends of the assembly. for steel e = 200 gpa and for brass e = 90 gpa. determine the total elongation for the assembly.