chapter+8+-+Rotation+-++Solutions.pdf

Conceptual Physics, 12e (Hewitt) Chapter 8 Rotational Motion 8.1 Multiple-Choice Questions 1) Horses with the greatest linear speed on a merry-go-round are located A) near the center. B) near the outside. C) anywhere, because they all move at the same speed. Answer: B Diff: 1 Topic: Circular Motio...

Conceptual Physics, 12e (Hewitt) Chapter 8 Rotational Motion 8.1 Multiple-Choice Questions 1) Horses with the greatest linear speed on a merry-go-round are located A) near the center. B) near the outside. C) anywhere, because they all move at the same speed. Answer: B Diff: 1 Topic: Circular Motion 2) Which horse moves faster in m/s on a merry-go-round? A) one near inner rail B) one near outer rail C) both move at the same speed in m/s. Answer: B Diff: 1 Topic: Circular Motion 3) If a turntable's rotational speed is doubled, then the linear speed of a pet hamster sitting on the edge of the record will A) double. B) halve. C) remain the same. Answer: A Diff: 1 Topic: Circular Motion 4) Your pet hamster sits on a record player that has constant angular speed. If the hamster moves to a point twice as far from the center, then its linear speed A) doubles. B) halves. C) remains the same. Answer: A Diff: 1 Topic: Circular Motion 5) When railroad tracks make a curve, the outer track is longer. This means a wheel that rides on the outer track needs to somehow A) roll slower than the wheel on the inner track. B) maintain the same speed as the wheel on the inner track. C) roll faster than the wheel on the inner track. Answer: C Diff: 1 Topic: Circular Motion 1 Copyright © 2015 Pearson Education, Inc. 6) When a train makes a curve, a tapered wheel rim is able to A) cover different distances per revolution. B) maintain a fixed rotational speed. C) reduce differences in angular speeds. Answer: A Diff: 1 Topic: Circular Motion 7) Each rolling wheel of a railroad train is tapered. Compared with the wide part, the narrow part of the wheel has a tangential speed that is A) less. B) greater. C) the same for both. Answer: A Diff: 1 Topic: Circular Motion 8) The tapered shape of the wheel rims that ride on railroad tracks allows opposite wheels to A) in effect, vary their diameters. B) travel at different linear speeds for the same rotational speed. C) both of these D) none of these Answer: C Diff: 1 Topic: Circular Motion 9) The circumference of a bicycle wheel is 2 meters. If it rotates at 1 revolution per second then its linear speed is A) 1 m/s. B) 2 m/s. C) 3 m/s. D) 3.14 m/s. E) 6.28 m/s. Answer: B Diff: 2 Topic: Circular Motion 10) Consider a string with several rocks tied along its length at equally spaced intervals. You whirl the string overhead so that the rocks follow circular paths. Compared with a rock at the end of the string, a rock at the middle moves A) half as fast. B) twice as fast. C) at the same linear speed. Answer: A Diff: 2 Topic: Circular Motion 2 Copyright © 2015 Pearson Education, Inc. 11) The net force exerted on a car traveling in a circular path at constant speed is A) directed forward, in the direction of travel. B) directed toward the center of the curve. C) zero because the car is not accelerating. D) none of the above Answer: B Diff: 2 Topic: Circular Motion 12) If you're on a Ferris wheel at a carnival, seated 10 m from the Ferris wheel's axis that makes a complete rotation each minute, your linear speed is A) 10 m/min. B) 31.4 m/min. C) 62.8 m/min. D) 100 m/min. E) need more information Answer: C Diff: 3 Topic: Circular Motion 13) The rotational inertia of your leg is greater when your leg is A) straight. B) bent. C) same either way Answer: A Diff: 1 Topic: Rotational Inertia 14) You can swing your legs to and fro more frequently when your legs are A) straight. B) bent. C) same either way Answer: B Diff: 1 Topic: Rotational Inertia 15) An industrial flywheel has a greater rotational inertia when most of its mass is A) nearer the rim. B) nearer the axis. C) uniformly spread out as in a disk. Answer: A Diff: 1 Topic: Rotational Inertia 3 Copyright © 2015 Pearson Education, Inc. 16) The rotational inertia of a pencil is greatest about an axis A) along its length, where the lead is. B) about its midpoint, like a propeller. C) about its end, like a pendulum. Answer: C Diff: 2 Topic: Rotational Inertia 17) Which of these animals has a quicker stride? A) giraffe B) horse C) cat D) mouse Answer: D Diff: 3 Topic: Rotational Inertia 18) A tightrope walker more easily balances on a tight wire if her pole A) is held high. B) droops. C) is short but heavy. Answer: B Diff: 2 Topic: Rotational Inertia 19) Consider two flywheels of the same size and shape, but one with twice the mass. Rotational inertia of the more massive one is A) two times greater. B) four times greater. C) the same as the other one. D) half. Answer: A Diff: 3 Topic: Rotational Inertia 20) A flywheel's diameter is twice that of another of the same shape and mass. Rotational inertia of the larger flywheel is A) two times greater. B) four times greater. C) the same as the other's. D) half. Answer: B Diff: 2 Topic: Rotational Inertia 4 Copyright © 2015 Pearson Education, Inc. 21) A coin and a ring roll down an incline at the same time. The one to first reach the bottom is the A) ring. B) coin. C) both reach the bottom at the same time Answer: B Diff: 2 Topic: Rotational Inertia 22) A ring and a disk both at rest roll down a hill together. Which rolls slower? A) ring B) disk C) depends on the masses D) both roll at the same speed E) need more information Answer: A Diff: 2 Topic: Rotational Inertia 23) A ring, a disk, and a solid sphere begin rolling down a hill together. Which reaches the bottom first? A) ring B) disk C) sphere D) all reach the bottom at the same time E) need more information Answer: C Diff: 2 Topic: Rotational Inertia 24) Stand a meterstick on its end and let it rotate to the floor. If you attach a heavy glob of clay to its upper end and repeat, the time to fall will be A) shorter. B) longer. C) the same. Answer: B Diff: 2 Topic: Rotational Inertia 25) A vertically-held sledge hammer is easier to balance when the heavier end is A) on your hand. B) at the top, away from your hand. C) the same either way Answer: B Diff: 2 Topic: Rotational Inertia 5 Copyright © 2015 Pearson Education, Inc. 26) Stand a broom upright on the end of its pole and let it topple to the floor. Repeat, but with the bristles end on the floor. The faster fall will be the broom standing on its A) pole-end. B) bristles-end. C) the same either way Answer: B Diff: 3 Topic: Rotational Inertia 27) Which jar will roll down an incline in the shortest time, an empty one or one filled with peanut butter? A) the empty jar B) both reach the bottom at the same time C) the filled jar D) need more information Answer: C Diff: 3 Topic: Rotational Inertia 28) Which tin can will roll down an incline in the shortest time, one filled with water or one filled with ice? (Hint: water 'slides' inside the can.) A) with water B) with ice C) both the same D) need more information Answer: A Diff: 3 Topic: Rotational Inertia 6 Copyright © 2015 Pearson Education, Inc. 29) Compared with a force, a torque involves A) rotation. B) leverage. C) distance from an axis of rotation. D) all the above Answer: D Diff: 1 Topic: Torque 30) A torque acting on an object tends to produce A) equilibrium. B) rotation. C) linear motion. D) velocity. E) a center of gravity. Answer: B Diff: 1 Topic: Torque 31) If Alex wishes to rotate his skateboard, then he must apply a A) torque. B) rotational maneuver. C) pause before bearing down on the board. Answer: A Diff: 1 Topic: Torque 32) A ball that gains speed as it rolls down a hill experiences a A) net torque. B) net force. C) both of these D) neither of these Answer: C Diff: 1 Topic: Torque 33) If you place a pipe over the end of a wrench when trying to rotate a stubborn bolt, effectively making the wrench handle twice as long, you'll multiply the torque by A) two. B) four. C) eight. Answer: A Diff: 1 Topic: Torque 7 Copyright © 2015 Pearson Education, Inc. 34) For a system in mechanical equilibrium, the resultant A) force must be zero. B) torque must be zero. C) both of these D) none of these Answer: C Diff: 2 Topic: Torque 35) A ball gains speed while rolling down a hill due mainly to A) its rotational inertia. B) its angular acceleration. C) a balanced torque. D) an unbalanced torque. Answer: D Diff: 2 Topic: Torque 36) To rotate a stubborn screw, it is best to use a screwdriver that has a A) wide handle. B) long handle. C) smooth handle. D) none of the above Answer: A Diff: 2 Topic: Torque 37) Two people are balanced on a seesaw. If one person leans inward toward the center of the seesaw, that person's end of the seesaw tends to A) rise. B) fall. C) stay at the same level. D) need more information Answer: A Diff: 2 Topic: Torque 38) On a balanced seesaw, a boy three times as heavy as his partner sits A) less than 1/3 the distance from the fulcrum. B) 1/3 the distance from the fulcrum. C) more than 1/3 the distance from the fulcrum. Answer: B Diff: 2 Topic: Torque 8 Copyright © 2015 Pearson Education, Inc. 39) A solitary boy cannot balance on a seesaw with its fulcrum at its midpoint. If the fulcrum is moved to one-quarter the distance from the boy, balance is achieved when the weight of the boy is A) less than the weight of the seesaw. B) equal to the weight of the seesaw. C) more than the weight of the seesaw. D) need more information Answer: C Diff: 3 Topic: Torque 40) A boy plays solitary seesaw by placing the seesaw's fulcrum one-eighth the distance from where he sits at one end. Which weighs more? A) the boy B) the seesaw C) they have equal weights D) need more information Answer: A Diff: 3 Topic: Torque 41) Toss a baseball bat into the air and it wobbles about its A) geometrical center. B) center of mass. C) heavier end. Answer: B Diff: 1 Topic: Center of Mass and Center of Gravity 42) The long, heavy tail of a spider monkey enables the monkey to easily vary its A) weight. B) momentum. C) inertia. D) center of gravity. E) none of the above Answer: D Diff: 1 Topic: Center of Mass and Center of Gravity 43) The center of mass of a human body is located at a point that A) is fixed, but different for different people. B) is always directly behind the belly button. C) changes as a person bends over. D) none of the above Answer: C Diff: 1 Topic: Center of Mass and Center of Gravity 9 Copyright © 2015 Pearson Education, Inc. 44) The famous Leaning Tower of Pisa doesn't topple over because its center of gravity is A) relatively low for such a tall building. B) stabilized by its structure. C) displaced from its center. D) above a place of support. E) in the same place as its center of mass. Answer: D Diff: 1 Topic: Center of Mass and Center of Gravity 45) Which of these has its center of mass where no mass exists? A) baseball B) golf ball C) basketball D) none of the above Answer: C Diff: 1 Topic: Center of Mass and Center of Gravity 46) If Earth had a pair of identical moons on opposite sides of the same circular orbit, the center of gravity of the double-moon-Earth system would be A) inside the Earth, but off center. B) at the center of the Earth. C) outside the Earth, but within the orbital path of the moons. D) outside the Earth, but beyond the orbital path of the moons. Answer: B Diff: 2 Topic: Center of Mass and Center of Gravity 47) To kick a football so it won't topple end over end, kick it so the force of impact extends A) above its center of gravity. B) through its center of gravity. C) below its center of gravity. Answer: B Diff: 2 Topic: Center of Mass and Center of Gravity 48) If Earth rotated more slowly about its axis, your weight would A) increase. B) decrease. C) stay the same. D) be zero. Answer: A Diff: 2 Topic: Center of Mass and Center of Gravity 10 Copyright © 2015 Pearson Education, Inc. 49) Strictly speaking, to weigh less in the Northern Hemisphere, you should move to a location farther A) north (toward the pole). B) south (toward the equator). C) east. D) west. Answer: B Diff: 2 Topic: Center of Mass and Center of Gravity 50) When riding at constant velocity on a Segway electric vehicle, your center of mass is A) slightly in front of the point between wheels below. B) slightly behind the point between wheels below. C) directly above the point between wheels below. Answer: C Diff: 2 Topic: Center of Mass and Center of Gravity 51) A 1-kg rock is suspended from the tip of a horizontal meterstick at the 0-cm mark so that the meterstick barely balances like a seesaw when its fulcrum is at the 25-cm mark. From this information, the mass of the meterstick is A) 1/4 kg. B) 1/2 kg. C) 3/4 kg. D) 1 kg. E) none of the above Answer: D Diff: 2 Topic: Center of Mass and Center of Gravity 52) A 1-kg rock is suspended from the tip of a horizontal meterstick at the 0-cm mark so that the meterstick barely balances like a seesaw when its fulcrum is at the 12.5-cm mark. From this information, the mass of the meterstick is A) 1/4 kg. B) 1/2 kg. C) 3/4 kg. D) 1 kg. E) none of the above Answer: E Diff: 3 Topic: Center of Mass and Center of Gravity 11 Copyright © 2015 Pearson Education, Inc. 53) You can safely stand on the overhanging end of a heavy plank that rests on a table. How much overhang depends on your mass and the plank's mass. If you can stand on the end of a plank that overhangs the edge of the supporting table 1/4 its total length, how massive is the plank compared to your mass? A) 1/2 B) the same C) 1 and 1/2 times D) twice E) 4 times Answer: B Diff: 3 Topic: Center of Mass and Center of Gravity 54) You can safely stand on the overhanging end of a heavy plank that rests on a table. How much overhang depends on your mass and the mass of the plank. If you can stand on the end of a plank that overhangs the edge of the supporting table 1/5 its total length, how massive is the plank compared to your mass? A) 1/3 B) the same C) 2/3 D) 1 and 1/3 times E) more than 1 and 1/3 times Answer: C Diff: 3 Topic: Center of Mass and Center of Gravity 55) If you balance a broom horizontally on one finger, the center of gravity of the broom will be above your finger, closer to the bristles end than the handle end. If you saw the broom in two pieces at that point and weigh the two parts on a scale, you'll find that the heavier part is the A) bristles part. B) handle part. C) both the same weight Answer: A Diff: 3 Topic: Center of Mass and Center of Gravity 56) The main reason a person weighs less at the equator than at the poles involves the A) spin of the Earth. B) influence of the Sun, Moon, and all the planets. C) law of action and reaction. Answer: A Diff: 1 Topic: Centripetal/Centrifugal Force 12 Copyright © 2015 Pearson Education, Inc. 57) Centrifugal forces are an apparent reality to observers in a reference frame that is A) moving at constant velocity. B) an inertial reference frame. C) at rest. D) rotating. E) none of the above Answer: D Diff: 1 Topic: Centripetal/Centrifugal Force 58) The force responsible for a car moving steadily along a no-friction icy banked curve is due to A) centrifugal effects. B) the normal force at right angles to the curved surface. C) the radial component of the normal force. D) none of the above Answer: C Diff: 2 Topic: Centripetal/Centrifugal Force 59) Centripetal force does no work on a circularly-moving object because A) no change in energy occurs. B) rotational energy transfers to kinetic energy. C) centripetal force has no component in the direction of motion. D) none of the above. Answer: C Diff: 2 Topic: Centripetal/Centrifugal Force 60) The bob of a conical pendulum swings in a A) to-and-fro path. B) circular path. C) chaotic path. Answer: B Diff: 2 Topic: Centripetal/Centrifugal Force 61) A difference between linear momentum and angular momentum involves A) a radial distance. B) two types of speed. C) both of these D) neither of these Answer: C Diff: 1 Topic: Angular Momentum 13 Copyright © 2015 Pearson Education, Inc. 62) Multiple the equation for linear momentum by radial distance r and you have A) rotational kinetic energy. B) angular momentum. C) rotational inertia. Answer: B Diff: 1 Topic: Angular Momentum 63) The gravitational field simulated by rotation in a space habitat that is best suited for humans is A) zero. B) g. C) one-quarter g. D) one-half g. E) three-quarters g. Answer: B Diff: 2 Topic: Angular Momentum 64) A swimming area in a rotating space habitat is located in a region of 1/4 g. If a diver can jump 1 m high in a 1-g region, how high can the same diver jump in the swimming area? A) 1 m B) 2 m C) 4 m D) 16 m E) more than 16 m Answer: C Diff: 3 Topic: Conservation of Angular Momentum 65) If the rotational speed of a rotating habitat in space increases, the weight experienced by occupants A) decreases. B) stays the same. C) increases. D) is always zero. Answer: C Diff: 2 Topic: Conservation of Angular Momentum 66) When a twirling ice skater brings her arms inward, her rotational speed A) decreases. B) remains the same. C) increases. Answer: C Diff: 1 Topic: Conservation of Angular Momentum 14 Copyright © 2015 Pearson Education, Inc. 67) The chef at the infamous Fattening Tower of Pizza tosses a spinning disk of uncooked pizza dough into the air. The disk becomes wider during its flight, while its rotational speed A) remains constant. B) quickens. C) slows. Answer: C Diff: 2 Topic: Conservation of Angular Momentum 68) When you do somersaults, you'll more easily rotate when your body is A) straight with both arms above your head. B) straight with both arms at your sides. C) curled into a ball shape. D) no difference Answer: C Diff: 2 Topic: Conservation of Angular Momentum 69) As a huge rotating cloud of particles in space gravitate together forming an increasingly dense ball, it shrinks in size and A) rotates slower. B) rotates at the same speed. C) rotates faster. D) cannot rotate. Answer: C Diff: 2 Topic: Conservation of Angular Momentum 70) If the planet Jupiter underwent gravitational collapse, its rate of rotation about its axis would A) decrease. B) increase. C) stay the same. D) need more information Answer: B Diff: 2 Topic: Conservation of Angular Momentum 71) As the polar icecaps melt, the resulting water spreads over the entire Earth. This new mass distribution tends to make the length of a day A) longer. B) shorter. C) none of these Answer: A Diff: 3 Topic: Conservation of Angular Momentum 15 Copyright © 2015 Pearson Education, Inc. 72) As you crawl toward the edge of a large freely-rotating horizontal turntable in a carnival funhouse, the angular momentum of you and the turntable A) decreases. B) increases. C) remains the same, but the revolutions per minute decrease. D) decreases in direct proportion to your decrease in revolutions per minute. E) none of these Answer: C Diff: 2 Topic: Conservation of Angular Momentum 16 Copyright © 2015 Pearson Education, Inc.