AP Physics B Work, Energy, & Oscillations 1. An applied force F pushes a block horizontally along a rough surface with force friction f. The resulting motion is constant velocity over a distance r. What is the net work? (A) W = Fr (D) W = µkmgr (B) W = fr (E) W = 0 (C) W = µsmgr 2. Which of the following results in zero net work being done on a mass m ? I. The mass remains at rest. II. The mass moves at constant velocity. III. Forces are unbalanced in the direction of initial velocity, but balanced perpendicular to the initial velocity. IV. Forces are balanced in the direction of initial velocity, but unbalanced perpendicular to the initial velocity. (A) I only (D) I, II, and III (B) II only (E) I, II, and IV (C) I and II N f F m Fg 3. Mass m, in the diagram, is accelerating to the right. Which of the following is true? (A) WF > Wf and WN > WFg (B) WF > Wf and WN < WFg (C) WF > Wf and WN = WFg (D) WF = Wf and WN = WFg (E) WF = Wf and WN > WFg N f m F θ Fg 4. 5. Mass m, in the diagram, is moving to the right at constant speed. Which of the following is true regarding the absolute value of each work? (A) WF > Wf and WN > WFg (B) WF > Wf and WN < WFg (C) WF > Wf and WN = WFg (D) WF = Wf and WN = WFg (E) WF = Wf and WN > WFg What conditions have to be met for work to be positive? (A) The force and displacement vectors must have the same direction. (B) A component of force must have the same direction as displacement. (C) The angle between force and displacement must be less than 90o and more than –90o. (D) Both A and B. (E) Both B and C. MC Sample 6. In order for an object to have useful potential energy (A) the potential energy must have a positive value. (B) the object must have energy associated with its position. (C) the object must be able to lose its potential energy when released. (D) the object must have kinetic energy as well. (E) the object must be stationary. 7. Car A has a mass m and moves at speed 2v, while car B has a mass 2m moves at speed v. What is the ratio of the kinetic energy of car A to that of car B? (A) 4 (D) 1/2 (B) 2 (E) 1/4 (C) 1 8. The work required to accelerate a car up a hill is equal to (A) the gravitational potential energy it acquires. (B) the kinetic energy it acquires. (C) the sum of the kinetic and potential energies. (D) the difference in the kinetic and potential energies. (E) None of these. 9. Which of the following is not true when conservative forces act? (A) The energy of the system remains constant. (B) Potential energy can increase or decrease. (C) The path an object moves dictates the value for work. (D) Conservative forces can increase or decrease the velocity of an object. (E) The net work is zero when an object moves at constant velocity. 2 kg 30o 20 m 10. A block starting at a height of 20 m above the ground slides down a smooth incline. What is the blocks speed when it reaches the ground? (A) 4 m/s (D) 20 m/s (B) 5 m/s (E) 40 m/s (C) 10 m/s 11. It requires a force F to stretch a spring a distance x. In the process an energy U is stored in the spring. If the spring is stretched 2x what is the force required and the energy stored? (A) 1F and 2U. (D) 4F and 4U. (B) 2F and 2U. (E) 4F and 8U. (C) 2F and 4U. 12. A kilowatt hour is a unit of (A) force / distance. (B) power. (C) energy / time. (D) work. (E) power / time. N 18. Which is the graph of kinetic energy in an oscillation? (A) (D) K K F f θ Fg x x 13. A mass moves a distance r horizontally along a rough surface as shown in the diagram. The applied force F is at an angle θ and is opposed by friction f. Which equation is incorrect? (D) Wg = mgr (A) WF = Frcosθ (E) All are correct. (B) Wf = −fr (C) WN = 0 (B) (E) K x x (C) K K o 14. You desire to lift an object 1 m. If you push it up a 30 incline which takes twice as long, compared to lifting it straight up, you do (A) half the work and require half the power. (B) half the work and require the same power. (C) the same work and require half the power. (D) the same work and require the same power. (E) twice the work with half the power. x 19. When mass is doubled the period of a spring (A) is doubled. (B) is halved. (C) is increased by a factor of 2 . (D) is decreases by a factor of 2 . (E) remains the same. 15. The area under a force-displacement graph is (A) work. (B) potential energy. (C) kinetic energy. (D) total mechanical energy. (E) power. 16. Which graph represents Hooke’s Law? (A) (D) F F x (B) Use this diagram for Questions 20 to 22 A B x C F x x F x 22. The restoring force is greatest at (A) A (B) B (C) C (D) A and C (E) A, B, and C 17. The period of a pendulum on Earth depends on (A) mass of the bob only. (B) length of the string only. (C) the vertical height that the bob moves through. (D) displacement of the bob from equilibrium. (E) length of the string and mass of the bob. E C C D E 6. 7. 8. 9. 10. −x 21. The potential energy is greatest at (A) A (B) B (C) C (D) A and C (E) A, B, and C (C) 1. 2. 3. 4. 5. m 20. The acceleration is least at (A) A (B) B (C) C (D) A and C (E) A, B, and C (E) F +x C B C C D 11. 12. 13. 14. 15. C D D C A 16. 17. 18. 19. 20. B B D C B 21. D 22. D

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