A uniform plank of length 4.0 m and weight 226 N rests horizontally on two supports, with 1.1 m of the plank hanging over the right support (see the drawing). To what distance x can a person who weighs 454 N walk on the overhanging part of the plank before it just begins to tip?

Question

sriram · Answer

wat drawing?

anonymous · Answer

attachment

sriram · Answer

conserve the torque 
226*1.1=454*x
x=1.1 / 2=5.5 m from the fulcrum

sriram · Answer

oops i m sorry but is there another fulcrum in the left??

anonymous · Answer

yeah- there is one on the far left then one 1.1 m from the right

sriram · Answer

i m so sorry i misread the question

sriram · Answer

k i got it 
there are 2 fulcrums or supports 
the support on the LHS ensures that the  plank won,t fall or rotate in anti clockwise direction.

sriram · Answer

so for movement to start it has to rotate in clockwise direction

sriram · Answer

hence for the torque eq. (look at support on RHS)
weight on its right= (1.1/4.0) *226 n at distance 1.1/2 from it
weight on its left=(2.9/4.0)*226 n at distance 2.9/2 from it

sriram · Answer

let d man be at a distance x on it's RHS
now write d torque eq..

sriram · Answer

(1.1/4)*226*(1.1/2) + x*454 = (2.9/4)*226*(2.9/2)
solve for x 
if man moves any further from this the plnck will rotate

sriram · Answer

i hope u  understood

sriram · Answer

good question