Problem: A 40kg, 5.0m long beam is supported by, but not attached to, the two posts in the figure. A 20kg boy starts walking along the beam. How close can he get to the right end of the beam without it falling over? My answer: \tau_net = (F_1*x_F_1)-(F_Beam*X_Beam)-(F_Boy*X_Boy) Since, \tau_net = 0 0 = (F_1*x_F_1)-(F_Beam*X_Beam)-(F_Boy*X_Boy) 0 = (40*3)-(40*2)-(20*X_boy) Comes out to X_Boy = 2? So the boy has to step at the very edge of the beam for it to start falling over?