# A rod with a ball attached is balanced?

An object is made by hanging a ball of mass $$M$$ from one end of a plank having the same mass and length $$L$$. The object is then pivoted at a point a distance $$L/4$$ from the end of the plank supporting the ball, as shown.

I would like to know why the above is true. Since $$\tau= \mid r \mid \mid F \mid \sin \theta$$, given that $$\sin \theta$$ is when $$\theta=90^{\circ}$$. The torque should then be $$\tau= rF$$ when assuming the axis to be a standard xy-plane. Am I supposed to figure out how $$F_g= \tau$$ where the some of the variables cancel? I don't really see it. How should I approach this problem to gain further understanding?