Calculate Distance of Man Walking on Plank Before Tipping

[ramalik]

A uniform plank of length 5.2 m and weight 213 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 445 N walk on the overhanging part of the plank before it just begins to tip?

I know you have to set the torque of the plank equal to the torque of the man and solve for his lever length. I just don't know how to get the torque of the plank.

 

[Doc Al]

I just don't know how to get the torque of the plank.

Where does the weight of the plank effectively act?

 

[ramalik]

the center! so i have to find the difference between the center point and the piece hanging off the side?

 

[Doc Al]

Yes. Hint: Choose the right support as the pivot point for calculating torques. How far from that point is the center of mass of the plank?

 

[ramalik]

2.6-1.1 = 1.5 m. Thanks!