Equilibrium Problem: Max Mass for Throckmorton on 6.0m Plank

[jghlee]

Homework Statement

A uniform wooden plank of length L = 6.0m and mass M = 90kg rests on top of two sawhorses separated by D = 1.5m, located equal distances from the center of the plank. Your cousin Throckmorton tries to stand on the right-hand end of the plank. If the plank is to remain at rest, how massive can Throckmorton be?

The Attempt at a Solution

How do I know the Xcg value for this problem since there are two sawhorses supporting this plank?

 

[rock.freak667]

Uniform means that the centre of gravity is at the geometrical centre of the plank. In this case, half of it's length.

 

[jghlee]

Uniform means that the centre of gravity is at the geometrical centre of the plank. In this case, half of it's length.

So even if there's a weight at the end of the plank, the center of gravity will still be at (L/2)?

 

[PhanthomJay]

So even if there's a weight at the end of the plank, the center of gravity will still be at (L/2)?

the cg of the plank is at L/2. The cg of the system (plank and cousin) changes, but you don't need to find it.