Question

Sphere X of mass M and charge +q hangs from a string as shown above. Sphere Y has an equal charge +q and is fixed in place a distance d directly below sphere X. If sphere X is in equilibrium, the tension in the string is most nearly

(A) Mg 

(B) Mg + kq/d 

(C) Mg – kq/d 

(D) Mg + kq²/d² 

(E) Mg – kq²/d²

Answer 1

The correct option is: (E) Mg – kq²/d²

Explanation:

ΣF = 0 so we have T + k(q)(q)/d² – Mg = 0 giving T = Mg – kq²/d²