# Two charges at the ends of a rod .

The figure shows a long, nonconducting, massless rod of length $$L$$, pivoted at its center and balanced with a block of weight $$W$$ at a distance $$x$$ from the left end. At the left and right ends of the rod are attached small conducting spheres with positive charges $$q$$ and$$2q$$, respectively. A distance h directly beneath each of these spheres is a fixed sphere with positive charge $$Q$$. The value $$h$$ should have so that the rod exerts no vertical force on the bearing when the rod is horizontal and balanced can be expressed as $\sqrt{ \frac{a qQ}{4 \pi \epsilon_{0} W}}$ what is the value of $$a+1$$.

×