Chapter 8. Rotational Motion

Angular displacement is usually express in units of
A) meters.
B) radians.
C) revolutions.
D) arcs.
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Angular displacement is usually express in units of
A) meters.
B) radians.
C) revolutions.
D) arcs.
B) radians.
Angular velocity is expressed in units of
A) meters per second.
B) radians per second.
C) omegas per second.
D) arcs per second.
B) radians per second.
Angular acceleration is expressed in units of
A) meters per second squared.
B) radians per second squared.
C) alphas per second squared.
D) arcs per second squared.
B) radians per second squared.
A boy and a girl are riding on a merry-go-round which is turning at a constant rate. The boy
is near the outer edge, and the girl is closer to the center. Who has the greater angular
displacement?
A) the boy
B) the girl
C) Both have the same non-zero angular displacement.
D) Both have zero angular displacement.
C) Both have the same non-zero angular displacement.
A boy and a girl are riding on a merry-go-round which is turning at a constant rate. The boy
is near the outer edge, and the girl is closer to the center. Who has the greater angular speed?
A) the boy
B) the girl
C) Both have the same non-zero angular velocity.
D) Both have zero angular velocity.
C) Both have the same non-zero angular velocity.
A boy and a girl are riding on a merry-go-round which is turning at a constant rate. The boy
is near the outer edge, and the girl is closer to the center. Who has the greater linear speed?
A) the boy
B) the girl
C) Both have the same non-zero translational velocity.
D) Both have zero translational velocity.
A) the boy
A boy and a girl are riding a merry-go-round which is turning at a constant rate. The boy is
near the outer edge, while the girl is closer to the center. Who has the greater centripetal
acceleration?
A) the boy
B) the girl
C) Both have the same non-zero centripetal acceleration.
D) Both have zero centripetal acceleration.
A) the boy
A boy and a girl are riding a merry-go-round which is turning at a constant rate. The boy is
near the outer edge, while the girl is closer to the center. Who has the greater tangential
acceleration?
A) the boy
B) the girl
C) Both have the same non-zero tangential acceleration.
D) Both have zero tangential acceleration.
D) Both have zero tangential acceleration.
Consider a rigid body that is rotating. Which of the following is an accurate statement?
A) Its center of rotation is its center of gravity.
B) All points on the body are moving with the same angular velocity.
C) All points on the body are moving with the same linear velocity.
D) Its center of rotation is at rest, i.e., not moving.
B) All points on the body are moving with the same angular velocity.
Rolling without slipping depends on
A) kinetic friction between the rolling object and the ground.
B) static friction between the rolling object and the ground.
C) tension between the rolling object and the ground.
D) the force of gravity between the rolling object and the Earth.
B) static friction between the rolling object and the ground.
Two equal forces are applied to a door. The first force is applied at the midpoint of the door; the second force is applied at the doorknob. Both forces are applied perpendicular to the door. Which force exerts the greater torque? A) the first at the midpoint B) the second at the doorknob C) both exert equal non-zero torques D) both exert zero torquesB) the second at the doorknobTwo equal forces are applied to a door at the doorknob. The first force is applied perpendicular to the door; the second force is applied at 30e to the plane of the door. Which force exerts the greater torque? A) the first applied perpendicular to the door B) the second applied at an angle C) both exert equal non-zero torques D) both exert zero torquesA) the first applied perpendicular to the doorTwo forces are applied to a doorknob, perpendicular to the door. The first force is twice as large as the second force. The ratio of the torque of the first to the torque of the second is A) 1/4. B) 1/2. C) 2. D) 4.C) 2.What is the quantity used to measure an object's resistance to changes in rotation? A) mass B) moment of inertia C) torque D) angular velocityB) moment of inertiaConsider two uniform solid spheres where both have the same diameter, but one has twice the mass of the other. The ratio of the larger moment of inertia to that of the smaller moment of inertia is A) 2. B) 8. C) 10. D) 4. E) 6.A) 2.Two uniform solid spheres have the same mass, but one has twice the radius of the other. The ratio of the larger sphere's moment of inertia to that of the smaller sphere is A) 4/5. B) 8/5. C) 2. D) 4.D) 4.Consider two uniform solid spheres where one has twice the mass and twice the diameter of the other. The ratio of the larger moment of inertia to that of the smaller moment of inertia is A) 2. B) 8. C) 4. D) 10. E) 6.B) 8.A uniform solid sphere has mass M and radius R. If these are increased to 2M and 3R, what happens to the sphere's moment of inertia about a central axis? A) increases by a factor of 6 B) increases by a factor of 12 C) increases by a factor of 18 D) increases by a factor of 54C) increases by a factor of 18If a constant net torque is applied to an object, that object will A) rotate with constant angular velocity. B) rotate with constant angular acceleration. C) having an increasing moment of inertia. D) having a decreasing moment of inertia.B) rotate with constant angular acceleration.The moment of inertia of a solid cylinder about its axis is given by 0.5 MR2. If this cylinder rolls without slipping, the ratio of its rotational kinetic energy to its translational kinetic energy is A) 1:1. B) 1:2. C) 2:1. D) 1:3.B) 1:2.Consider a motorcycle of mass 150 kg, one wheel of which has a mass of 10 kg and a radius of 30 cm. What is the ratio of the rotational kinetic energy of the wheels to the total translational kinetic energy of the bike? Assume the wheels are uniform disks. A) 0.033:1 B) 0.067:1 C) 0.33:1 D) 0.67:1B) 0.067:1Suppose a solid sphere of mass M and radius R rolls without slipping down an inclined plane starting from rest. The linear velocity of the sphere at the bottom of the incline depends on A) the mass of the sphere. B) the radius of the sphere. C) both the mass and the radius of the sphere. D) neither the mass nor the radius of the sphere.D) neither the mass nor the radius of the sphere.Suppose a solid sphere of mass M and radius R rolls without slipping down an inclined plane starting from rest. The angular velocity of the sphere at the bottom of the incline depends on A) the mass of the sphere. B) the radius of the sphere. C) both the mass and the radius of the sphere. D) neither the mass nor the radius of the sphere.B) the radius of the sphere."The total angular momentum of a system of particles changes when a net external force acts on the system." This statement is A) always true. B) never true. C) sometimes true. It depends on the force's magnitude. D) sometimes true. It depends on the force's point of application.D) sometimes true. It depends on the force's point of application.In what circumstances can the angular velocity of system of particles change without any change in the system's angular momentum? A) This cannot happen under any circumstances. B) This can happen if a net external force acts on the system's center of mass. C) This can happen if the only forces acting are internal to the system. D) This can happen if an external net torque is applied properly to the system.C) This can happen if the only forces acting are internal to the system.The Earth orbits the Sun in an elliptical orbit. Ignore any friction which may be present. What happens over time to the Earth's angular momentum about the Sun? A) It continually increases. B) It continually decreases. C) It remains constant. D) It increases during some parts of the orbit, and decreases during others.C) It remains constant.The Earth moves about the Sun in an elliptical orbit. As the Earth moves close to the Sun, then which of the following best describes the orbiting speed of the Earth about the Sun? A) increases B) decreases C) remains constant D) none of the aboveA) increasesAn ice skater performs a pirouette (a fast spin) by pulling in his outstretched arms close to his body. What happens to his angular momentum about the axis of rotation? A) It does not change. B) It increases. C) It decreases. D) It changes, but it is impossible to tell which way.A) It does not change.An ice skater performs a pirouette (a fast spin) by pulling in his outstretched arms close to his body. What happens to his rotational kinetic energy about the axis of rotation? A) It does not change. B) It increases. C) It decreases. D) It changes, but it is impossible to tell which way.B) It increases.An ice skater performs a pirouette (a fast spin) by pulling in his outstretched arms close to his body. What happens to his moment of inertia about the axis of rotation? A) It does not change. B) It increases. C) It decreases. D) It changes, but it is impossible to tell which way.C) It decreases.