I need two answers for this question. Also, please explain why. Thank you. 131.
ID: 778505 • Letter: I
Question
I need two answers for this question. Also, please explain why. Thank you.
131. Two hollow, uncharged conducting spheres hang by threads from the ceiling, as shown above. The spheres have the same mass but are different sizes. A charge +Q is deposited on the larger sphere. The spheres are then momentarily brought into contact and separated, after which they move away from each other. Which of the following statements about the final state of the spheres and strings must be true? Select two answers. (A) The spheres have charges of opposite sign. (B) The sum of the charges on the spheres is +Q. (C) The tension in each string is larger than it was initially (D) The force exerted by the ceiling on each string is directed vertically upward.Explanation / Answer
as the spheres repel each other , the charges on each sphere has same sign.
hence option A is wrong.
using conservation of charge principle, total charge will remain conserved
hence option B is correct.
earlier, tension=weight of the sphere
after ,
as each string now makes some angle with vertical, let the angle be theta.
if tension is T
T*cos(theta)=weight of the sphere
as cos(theta) < 1,
T > weight of the sphere
hence tension in each string is larger than it was initially.
hence option C is correct.
as each string makes some angle with vertical, force exerted by the ceiling is along the string and can not be directed vertically upward.
hence option D is incorrect.
so correct options are:
option B
option C