A Pendulum Bob Has Potential Energy U₀ When Held Taut

Multiple Choice

A pendulum bob has potential energy U₀ when held taut in a horizontal position. The bob falls until it is 30° away from the horizontal position, when it has potential energy U_A. It continues to fall until the string is vertical, when it has potential energy U_B. Compare its potential energies at O, A, and B.

A) U₀ = U_A = U_B.
B) U_A − U_B = 2U₀.
C) U_A − U_B = U₀ − U_A.
D) U₀ = U_B = 2U_A.
E) U₀ − U_A = 2(U_A − U_B) .