Two initially uncharged identical metal spheres 1 and 2 are connected by an insulating spring (unstretched length of 0.68 m).Charge +6.2 $\mu$C is placed on the first sphere and -6.2 $\mu$C on the second sphere,causing the spring to contract to a length of 0.43 m.If someone coats the spring with metal to make it conducting,what is the new length of the spring? Recall that the force exerted by a spring is k$\Delta$x,where $\Delta$x is the change in the spring's length from its unstretched/uncompressed length.
A)0.25 m
B)0.43 m
C)0.56 m
D)0.68 m
E)0.75 m

Question

Quizplus · Accepted Answer

Since the metal spheres have an equal and opposite charge, they will attract each other and the spring will contract until the electrostatic force balances the spring force. When the spring is coated with metal, it becomes a conductor and the charges on the spheres will distribute themselves evenly on the outside surfaces of the metal spheres. This will effectively eliminate the electrostatic force between the spheres and the spring will be extended to its original unstretched length of 0.68 m. Therefore, the new length of the spring is 0.68 m.

Two Initially Uncharged Identical Metal Spheres 1 and 2 Are μ\muμ

Two Initially Uncharged Identical Metal Spheres 1 and 2 Are $\mu$