Rotational Motion Answer Key

Conceptual Physics 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 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 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 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 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 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 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 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 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 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 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 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 13) The rotational inertia of your leg is greater when your leg is A) straight. B) bent. C) same either way Answer: A 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 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 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 17) Which of these animals has a quicker stride? A) giraffe B) horse C) cat D) mouse Answer: D 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 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 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