Physics Conceptual MC chap 9

A 2.0-kg hoop rolls without slipping on a horizontal surface so that its center proceeds to the right with a constant linear speed of 6.0 m/s. 53. Which one of the following statements is true concerning the angular momentum of this hoop? A) It points into the paper. B) It points out of the paper. C) It points to the left. D) It points to the right. E) It varies from point to point on the hoop.

A) It points into the paper.

24. Two uniform solid spheres, A and B have the same mass. The radius of sphere B is twice that of sphere A. The axis of rotation passes through each sphere. Which one of the following statements concerning the moments of inertia of these spheres is true? A) The moment of inertia of A is one-fourth that of B. B) The moment of inertia of A is one-half that of B. C) The moment of inertia of A is 5/4 that of B. D) The moment of inertia of A is 5/2 that of B. E) The two spheres have equal moments of inertia.

A) The moment of inertia of A is one-fourth that of B.

30. A solid sphere and a hollow sphere each of mass M and radius R are released at the same time from the top of an inclined plane. Which one of the following statements is necessarily true? A) The solid sphere will reach the bottom first. B) The hollow sphere will reach the bottom first. C) Both spheres will reach the bottom at the same time. D) The solid sphere will reach the bottom with the greater kinetic energy. E) The hollow sphere will reach the bottom with the greater kinetic energy.

A) The solid sphere will reach the bottom first.

23. Which one of the following statements concerning the moment of inertia I is false? A) I may be expressed in units of kg ⋅ m2. B) I depends on the angular acceleration of the object as it rotates. C) I depends on the location of the rotation axis relative to the particles that make up the object. D) I depends on the orientation of the rotation axis relative to the particles that make up the object. E) Of the particles that make up an object, the particle with the smallest mass may contribute the greatest amount to I.

B) I depends on the angular acceleration of the object as it rotates.

42. A spinning star begins to collapse under its own gravitational pull. Which one of the following occurs as the star becomes smaller? A) The star's angular velocity decreases. B) The star's angular momentum remains constant. C) The star's angular momentum increases. D) The star's angular velocity remains constant. E) Both the star's angular momentum and its angular velocity remain constant.

B) The star's angular momentum remains constant.

29. A hollow cylinder of mass M and radius R rolls down an inclined plane. A block of mass M easily slides down an identical inclined plane. Complete the following statement: If both objects are released at the same time from the top of their inclined planes, A) the cylinder will reach the bottom first. B) the block will reach the bottom first. C) the block will reach the bottom with the greater kinetic energy. D) the cylinder will reach the bottom with the greater kinetic energy. E) both the block and the cylinder will reach the bottom at the same time.

B) the block will reach the bottom first.

41. What happens when a spinning ice skater draws in her outstretched arms? A) Her angular momentum decreases. B) Her angular momentum increases. C) Her moment of inertia decreases causing her to speed up. D) Her moment of inertia decreases causing her to slow down. E) The torque that she exerts increases her moment of inertia.

C) Her moment of inertia decreases causing her to speed up.

49. A ball of mass M moves in a circular path on a horizontal, frictionless surface. It is attached to a light string that passes through a hole in the center of the table. If the string is pulled down, thereby reducing the radius of the path of the ball, the speed of the ball is observed to increase. Complete the following sentence: This occurs because A) the linear momentum of the ball is conserved. B) it is required by Newton's first law of motion. C) the angular momentum of the ball is conserved. D) the angular momentum of the ball must increase. E) the total mechanical energy of the ball must remain constant.

C) the angular momentum of the ball is conserved.

17. Consider the following four objects: a hoop, a flat disk, a solid sphere, and a hollow sphere. Each of the objects has mass M and radius R. The axis of rotation passes through the center of each object, and is perpendicular to the plane of the hoop and the plane of the flat disk. Which of these objects requires the largest torque to give it the same angular acceleration? A) the solid sphere B) the hollow sphere C) the hoop D) the flat disk E) both the solid and the hollow spheres

C) the hoop

40. A child standing on the edge of a freely spinning merry-go-round moves quickly to the center. Which one of the following statements is necessarily true concerning this event and why? A) The angular speed of the system decreases because the moment of inertia of the system has increased. B) The angular speed of the system increases because the moment of inertia of the system has increased. C) The angular speed of the system decreases because the moment of inertia of the system has decreased. D) The angular speed of the system increases because the moment of inertia of the system has decreased. E) The angular speed of the system remains the same because the net torque on the merry-go-round is zero N ⋅ m.

D) The angular speed of the system increases because the moment of inertia of the system has decreased.

55. A compact disc rotates about its center at constant angular speed. Which one of the following quantities is constant and non-zero for a dust particle near the edge of the disc? A) linear velocity B) torque about the center of the disc C) centripetal acceleration D) angular momentum E) angular acceleration

D) angular momentum

5. Complete the following statement: A body is in translational equilibrium A) only if it is at rest. B) only if it is moving with constant velocity. C) only if it is moving with constant acceleration. D) if it is either at rest or moving with constant velocity. E) if it is moving with either constant velocity or constant acceleration.

D) if it is either at rest or moving with constant velocity.

13. Which one of the following statements most accurately describes the center of gravity of an object? A) It is the point where gravity acts on the object. B) It is the point where all the mass is concentrated. C) It must be experimentally determined for all objects. D) It is the point on the object where all the weight is concentrated. E) It is the point from which the torque produced by the weight of the object can be calculated.

E) It is the point from which the torque produced by the weight of the object can be calculated.

1. Complete the following statement: When a net torque is applied to a rigid object, it always produces a A) constant acceleration. B) rotational equilibrium. C) constant angular velocity. D) constant angular momentum. E) change in angular velocity.

E) change in angular velocity.