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## Homework Statement

a uniform 12.0m long board has mass 500kg. it rest 5.5m over a cliff. How far can a 80kg man walk on the board before it tips?

## Homework Equations

equilibrium and torque

## The Attempt at a Solution

im not quite sure about any portion of my work, because i resorted to canceling units to produce the one that made sense.

[tex]W_{board}=500kg\cdot9.8=4.9\cdot10^{3}N[/tex]

[tex]W_{man}=80kg\cdot9.8=784N[/tex]

the fulcrum is at at position: 12.0m-5.5m = 6.5m

torques must be equal so,

[tex]\tau_{clockwise}=\tau_{counterclockwise}[/tex]

[tex]\left(L_{1}\right)\left(784N\right)=\left(4.9\cdot10^{3}N\right)\left(.5m\right)[/tex]

[tex]\left(L_{1}\right)=\frac{\left(4.9\cdot10^{3}N\right)\left(.5m\right)}{784N}=3.1m[/tex]

so, the man can stand 3.1m from the fulcrum on the side over the cliff?

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