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X - A Questions 21-22. A block on a horizontal frictionless plane is attached to a spring, as shown above. The block oscillates along the x-axis with simple harmonic motion of amplitude A. 21. Which of the following statements about the block is correct? (A) At x = 0, its acceleration is at a maximum. (B) At x = A, its displacement is at a maximum. (C) At x = A, its velocity is at a maximum. (D) At x = A, its acceleration is zero. 22. Which of the following statements about energy is correct? (A) The potential energy of the spring is at a minimum at x = 0. (B) The potential energy of the spring is at a minimum at x = A. (C) The kinetic energy of the block is at a minimum at x =0. (D) The kinetic energy of the block is at a maximum at x = A. 23. A simple pendulum consists of a 1.0 kilogram brass bob on a string about 1.0 meter long. It has a period of 2.0 seconds. The pendulum would have a period of 1.0 second if the (A) string were replaced by one about 0.25 meter long (B) string were replaced by one about 2.0 meters long (C) bob were replaced by a 0.25 kg brass sphere (D) bob were replaced by a 4.0 kg brass sphere 24. A pendulum with a period of 1 s on Earth, where the acceleration due to gravity is g, is taken to another planet, where its period is 2 s. The acceleration due to gravity on the other planet is most nearly (A) g/4 (B) 8/2 (C) 2g (D) 4g M 25. An ideal massless spring is fixed to the wall at one end, as shown above. A block of mass M attached to the other end of the spring oscillates with amplitude A on a frictionless, horizontal surface. The maximum speed of the block is vm. The force constant of the spring is Mg Mgvm MVm My2 (A) A (B) (C) 2A 2A (D) - A 2