- #1
gcombina
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Homework Statement
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
Homework Equations
T = Force x level arm
The Attempt at a Solution
T = F x Lmg 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!