A beam, uniform in mass, M = 65.1 kg and length L = 28.2 m, hangs by a cable supported at point B, and rotates without friction around point A. On the end far of the beam, an object of mass m = 10.8 kg is hanging. The beam is making an angle of θ = 32.9° at point A with respect to the + x-axis. The cable makes an angle φ = 27.6° with respect to the - x-axis at B. Assume ψ = θ + φ.

Enter an expression for the lever arm for the weight of the beam, lB, about the point A.