7. When submitted to a net torque of 6.2 Nm, the 11. In which of the following situations is the angular wheel of a scooter increases its angular speed from momentum of the system conserved? 1.4 rad/s to 4.7 rad/s in 4.5 s. What is the rotational inertia of the wheel? VA. A cylinder that rotates about its axis with a net zero torque A. 2.2 N.mz B. A cylinder that rotates about its axis due to a B. 3.8 N.mz net torque of 25 N.m C. 5.6 N.m C. A cylinder that rotates about it axis and then stops because of friction V D. 8.5 N.m D. A toy car that moves on an inclined plane due E. 13 N.m a net force of 25 N B. A constant net non-zero torque is exerted on an E. A toy car that moves on an inclined plane with zero net force object. Which of the following quantities cannot be constant for this object? 12. A student initially stands on a circular platform 1. Angular velocity that is free to rotate without friction about its center. II. Angular acceleration The student jumps off tangentially, setting the Angular momentum platform spinning. Quantities that are conserved for the student-platform system as the student jumps A. Ionly include which of the following? B. II only I. Angular momentum C. III only II. Linear momentum V D. I and III only III. Kinetic energy E. II and III only V A. I only 9. What is/are the condition (s) for the angular B. II only momentum to be conserved? I. Net torque must be zero C. I and II only II. Angular velocity must be constant D. II and III only III. Change in angular momentum must be zero E. I, II and III A. I only B. II only 13. A hockey puck traveling at a speed of v on essentially frictionless ice collides elastically with one C. III only end of a straight stick lying on the ice. In this V D. I and III only collision, which of the following is/are correct? E. II and III only 1. Momentum is conserved II. Angular momentum is conserved 10. Which of the following must be true in order for a III. Energy is conserved rotating platform to continue rotating with a constant angular velocity? A. I only A. There are no forces exerted on it B. II only B. There is no friction exerted on it C. III only C. There is zero net force exerted on it D. I and II only D. There are no torques exerted on it V E. I, II and III V E. There is zero net torque exerted on it14. A disk is sliding on a horizontal surface that has 17. Suppose that a spherical star spinning at an initial negligible friction collides with a rod that is free to angular velocity @ suddenly collapses to half of its move and rotate on the surface, as shown in the top original radius without any loss of mass. Assume the view below. Which of the following quantities must star has uniform density before and after the be the same for the disk-rod system before and after collapse. What will the angular velocity of the star be the collision? after the collapse? I. Linear momentum II. Angular momentum A. w/4 III. Kinetic energy B. w/2 Surface C. w A. I only D. 20 B. II only O- V E 40 V C. I and II only D. II and III only Top View 18. When a woman on a frictionless rotating turntable extends her arms out horizontally, her E. I, II and III angular momentum. 15. A figure skater goes into spin with arms fully A. must increase extended. Which of the following describes the changes in the rotational kinetic energy and angular B. must decrease momentum of the skater as the skater's arms are V C. must remain the same brought toward the body? D. may increase or decrease depending on her initial angular velocity Rotational kinetic Angular energy momentum E. tilts away from the vertical A. Remains the same Increases B. Remains the same Remains the same 19. A spinning ice skater on extremely smooth ice is able to control the rate at which she rotates by V C. Increases Remains the same pulling in her arms. Which of the following D. Decreases Increases statements is/are true about the skater during this E Decreases Remains the same process I. Her angular momentum remains constant. 16. Stars originate as large bodies of slowly rotating II. Her moment of inertia remains constant. gas. Because of gravity, these clumps of gas slowly III. She is subject to a constant non-zero torque. decrease in size. The angular velocity of a star increases as it shrinks because of _ V A. Ionly A. conservation of mass B. II only B. conservation of energy C. II only C. the law of universal gravitation D. I and III only D. conservation of linear momentum E. II and Ill only V E. conservation of angular momentum