SAT Subject Physics Practice Question 375: Answer and Explanation
71. The kinetic energy a pendulum contains 74. Einstein's theory of relativity is based on when it passes through its zero displacement may be decreased by
A. increasing the mass of the bob.
B. increasing the thickness of the string.
C. decreasing the length of the string.
D. increasing the length of the string.
E. decreasing the displacement of the
Correct Answer: E
The correct answer is (E). When the pendulum is displaced, the potential energy the pendulum gains is equal to the height above the zero point to which the pendulum is raised. When the pendulum is released, all the potential energy at its displaced position is converted into kinetic energy. Thus, a smaller displacement gives the pendulum less potential energy, which in turn yields less kinetic energy when the bob moves through the zero point.