Aperson carries a plank of wood 2.00 m long with one hand pushing down on it at one end with a force f1 and the other hand holding it up at .500 m from the end of the plank with force f2 . if the plank has a mass of 20.0 kg and its center of gravity is at the middle of the plank, what is the magnitude of the force f1?

Explanation:

Given:

For the plank to be in equilibrium the total sum of total forces & moments (about any point) must be zero:

&

We take the sum of forces:

.............................................(1)

Take moment about the extreme right:

Now, put this value in eq. (1)

i think the answer would be b

if the person is shown to have +90n, then ans is -10n.

if the person is shown to have -90n, then ans is +10n.