1. The problem statement, all variables and given/known data A horizontal, 10-m plank weighs 100 N. It rests on two supports that are placed 1.0 m from each end as shown in the figure. How close to one end can an 800-N person stand without causing the plank to tip? (a) 0 m (d) 0.7 m (b) 0.3 m (e) 0.9 m (c) 0.5 m 2. Relevant equations T = Force x level arm 3. The attempt at a solution T = F x L mg x (center of gravity of the plank) = mg x level arm [ (90N)(9.8) ] ( 4.5 ) = [ (800N)(9.8) ] ( l ) level arm = .5 My question is why do "center of mass" needs to be used? I originally did 90N but didn't work so I had to do 4.5 for the center of mass Thanks!