ch08 - Chapter 8: POTENTIAL ENERGY AND CONSERVATION OF...

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Unformatted text preview: Chapter 8: POTENTIAL ENERGY AND CONSERVATION OF ENERGY 1. Only if a force on a particle is conservative: A. is its work zero when the particle moves exactly once around any closed path B. is its work always equal to the change in the kinetic energy of the particle C. does it obey Newton’s second law D. does it obey Newton’s third law E. is it not a frictional force ans: A 2. A nonconservative force: A. violates Newton’s second law B. violates Newton’s third law C. cannot do any work D. must be perpendicular to the velocity of the particle on which it acts E. none of the above ans: E 3. The sum of the kinetic and potential energies of a system of objects is conserved: A. only when no external force acts on the objects B. only when the objects move along closed paths C. only when the work done by the resultant external force is zero D. always E. none of the above ans: E 4. A force on a particle is conservative if: A. its work equals the change in the kinetic energy of the particle B. it obeys Newton’s second law C. it obeys Newton’s third law D. its work depends on the end points of every motion, not on the path between E. it is not a frictional force ans: D 5. Two particles interact by conservative forces. In addition, an external force acts on each particle. They complete round trips, ending at the points where they started. Which of the following must have the same values at the beginning and end of this trip? A. the total kinetic energy of the two-particle system B. the potential energy of the two-particle system C. the mechanical energy of the two-particle system D. the total linear momentum of the two-particle system E. none of the above ans: B 102 Chapter 8: POTENTIAL ENERGY AND CONSERVATION OF ENERGY 6. Two objects interact with each other and with no other objects. Initially object A has a speed of 5 m / s and object B has a speed of 10 m / s. In the course of their motion they return to their initial positions. Then A has a speed of 4 m / s and B has a speed of 7 m / s. We can conclude: A. the potential energy changed from the beginning to the end of the trip B. mechanical energy was increased by nonconservative forces C. mechanical energy was decreased by nonconservative forces D. mechanical energy was increased by conservative forces E. mechanical energy was decreased by conservative forces ans: C 7. A good example of kinetic energy is provided by: A. a wound clock spring B. the raised weights of a grandfather’s clock C. a tornado D. a gallon of gasoline E. an automobile storage battery ans: C 8. No kinetic energy is possessed by: A. a shooting star B. a rotating propeller on a moving airplane C. a pendulum at the bottom of its swing D. an elevator standing at the f fth F oor E. a cyclone ans: D 9. The wound spring of a clock possesses: A. kinetic but no potential energy B. potential but no kinetic energy C. both potential and kinetic energy in equal amounts D. neither potential nor kinetic energy E. both potential and kinetic energy, but more kinetic energy than potential energyE....
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