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Why is the following situation impossible? In a large city with an air-pollution problem, a bus has no combustion engine. It runs over its citywide route on energy drawn from a large, rapidly rotating flywheel under the floor of the bus. The flywheel is spun up to its maximum rotation rate of 3 000 rev/min by an electric motor at the bus terminal. Every time the bus speeds up, the flywheel slows down slightly. The bus is equipped with regenerative braking so that the flywheel can speed up when the bus slows down. The flywheel is a uniform solid cylinder with mass 1 200 kg and radius 0.500 m. The bus body does work against air resistance and rolling resistance at the average rate of 25.0 hp as it travels its route with an average speed of 35.0 km/h.
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Chapter 10 Solutions
EBK PHYSICS FOR SCIENTISTS AND ENGINEER
- Why is the following situation impossible? A space station shaped like a giant wheel has a radius of r = 100 m and a moment of inertia of 5.00 108 kg m2. A crew of 150 people of average mass 65.0 kg is living on the rim, and the stations rotation causes the crew to experience an apparent free-fall acceleration of g (Fig. P10.52). A research technician is assigned to perform an experiment in which a ball is dropped at the rim of the station every 15 minutes and the time interval for the ball to drop a given distance is measured as a test to make sure the apparent value of g is correctly maintained. One evening, 100 average people move to the center of the station for a union meeting. The research technician, who has already been performing his experiment for an hour before the meeting, is disappointed that he cannot attend the meeting, and his mood sours even further by his boring experiment in which every time interval for the dropped ball is identical for the entire evening.arrow_forwardLara is running just outside the circumference of a carousel, looking for her favorite horse to ride, with a constant angular speed of 1.00 rad/s. Just as she spots the horse, one-fourth of the circumference ahead of her, the carousel begins to move, accelerating from rest at 0.050 rad/s2. a. Taking the time when the carousel begins to move as t = 0, when will Lara catch up to the horse? b. Lara mistakenly passes the horse and keeps running at constant angular speed. If the carousel continues to accelerate at the same rate, when will the horse draw even with Lara again?arrow_forwardA disk with moment of inertia I1 rotates about a frictionless, vertical axle with angular speed i. A second disk, this one having moment of inertia I2 and initially not rotating, drops onto the first disk (Fig. P10.50). Because of friction between the surfaces, the two eventually reach the same angular speed f. (a) Calculate f. (b) Calculate the ratio of the final to the initial rotational energy. Figure P10.50arrow_forward
- Why is the following situation impossible? A space station shaped like a giant wheel (Fig. P11.28, page 306) has a radius of r = 100 m and a moment of inertia of 5.00 108 kg m2. A crew of 150 people of average mass 65.0 kg is living on the rim, and the stations rotation causes the crew to experience an apparent free-fall acceleration of g. A research technician is assigned to perform an experiment in which a ball is dropped at the rim of the station every 15 minutes and the time interval for the ball to drop a given distance is measured as a lest to make sure the apparent value of g is correctly maintained. One evening, 100 average people move to the center of the station for a union meeting. The research technician, who has already been performing his experiment for an hour before the meeting, is disappointed that he cannot attend the meeting, and his mood sours even further by his boring experiment in which every time interval for the dropped ball is identical for the entire evening. Figure P11.28arrow_forwardPlease answer this within 30 mins ! I will upvote !arrow_forwardThe wheel in the figure has eight equally spaced spokes and a radius of 50 cm. It is mounted on a fixed axle and is spinning at 3.7 rev/s. You want to shoot a 23-cm-long arrow parallel to this axle and through the wheel without hitting any of the spokes. Assume that the arrow and the spokes are very thin. What minimum speed must the arrow have? Number Units Use correct number of significant digits; the tolerance is +/-2%arrow_forward
- Consider a 50.0 kg merry go round with a radius of 1.50 rotating at 20.0 rpm with an 18.0 kg child located 1.25 m from the center. What is the total kinetic energy of the system? Group of answer choices 74.0 J 185 J 296 J 307 Jarrow_forwardA solid sphere with a diameter of 0.17 m is released from rest; it then rolls without slipping down a ramp, dropping through a vertical height of 0.61 m. The ball leaves the bottom of the ramp, which is 1.22 m above the floor, moving horizontally. a) Through what horizontal distance d does the ball move before landing? b) How many revolutions does the ball make during its fall? c) If the ramp were to be made frictionless, would the distance d increase, decrease, or stay the same? Explain.arrow_forwardYour grandmother enjoys creating pottery as a hobby. She uses a potter’s wheel, which is a stone disk of radius R = 0.500 m and mass M = 100 kg. In operation, the wheel rotates at 50.0 rev/min. While the wheel is spinning, your grandmother works clay at the center of the wheel with her hands into a pot-shaped object with circular symmetry. When the correct shape is reached, she wants to stop the wheel in as short a time interval as possible, so that the shape of the pot is not further distorted by the rotation. She pushes continuously with a wet rag as hard as she can radially inward on the edge of the wheel and the wheel stops in 6.00 s. (a) You would like to build a brake to stop the wheel in a shorter time interval, but you must determine the coefficient of friction between the rag and the wheel in order to design a better system. You determine that the maximum pressing force your grandmother can sustain for 6.00 s is 70.0 N. (b) What If? If your grandmother instead chooses to press…arrow_forward
- Question 8. A flywheel is a solid disk that rotates about an axis that is perpendicular to the disk at its center. Rotating flywheels provide a means for storing energy in the form of rotational kinetic energy and are being considered as a possible alternative to batteries in electric cars. The gasoline burned in a 414-mile trip in a typical midsize car produces about 1.32 × 109 J of energy. How fast would a 44.1-kg flywheel with a radius of 0.304 m have to rotate to store this much energy? Give your answer in rev/min. Ans: 343712.61 rev/minarrow_forwardA circular bird feeder 19 cm in radius has rotational inertia 0.12kg·m2. The feeder is suspended horizontally by a thin wire through the middle, and is spinning slowly at 6.1 rpm. A 140 g bird lands on the rim of the feeder, coming in tangent to the rim at 1.1 m/s in a direction opposite the feeder’s rotation. Assume the feeder-bird system is isolated; no pFBD or IST is required for this problem. Please put your answers in terms of the variables listed. Variables: R-radius of feeder I0-Feeder inertia w0-initial angular velocity m-bird mass v0-bird initial speed Lbird-bird intitial angular momentum Iafter-system final inertia wf-final angular velocity q. Treat the bird as a point-particle, and define the feeder’s initial rotation direction to be positive. Write an expression in terms of given variables for the bird’s angular momentum immediately before contact with the feeder about the feeder’s axis of rotation Lbird in terms of the variables above.arrow_forwardMary and her younger brother Alex decide to ride the carousel at the State Fair. Mary sits on one of the horses in the outer section at a distance of 2.0 m from the center. Alex decides to play it safe and chooses to sit in the inner section at a distance of 1.3 m from the center. The carousel takes 5.0 s to make each complete revolution. (a) What is Mary's angular speed ?M and tangential speed vM? ?M _____rev/svM =_____m/s (b) What is Alex's angular speed ?A and tangential speed vA? ?A _____rev/svA =_____m/sarrow_forward
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