Sample HW07 - PHYS 21800 This print-out should have 13 questions. Multiple-choice questions may continue on the next column or page – find all choices before answering. Tipler PSE5 09 43 B 001 (part 1 of 2) 10.0 points Four particles with masses 9 kg, 5 kg, 7 kg, and 4 kg are connected by rigid rods of negligible mass as shown. The origin is centered on the mass in the lower-left corner. The rectangle is 7 m wide and 4 m long. y 9 kg 4 kg 1 while accelerating? Holt SF 08Rev 68 005 (part 1 of 3) 10.0 points A pulley has a moment of inertia of 3 kg m2 and a radius of 1.1 m . A cord is wrapped over the pulley and attached to a hanging object on either end. Assume the cord does not slip, the axle is frictionless, and the two hanging objects have masses of 3 kg and 7 kg . Find the acceleration of each mass. The acceleration of gravity is 9.81 m/s2 . 4m Correct answer: 3.1444 m/s2 . 5 rad/s 5 kg 7m x 006 (part 2 of 3) 10.0 points Find the force in the cord supporting the smaller mass. 7 kg If the system rotates in the xy plane about the z axis (origin, O) with an angular speed of 5 rad/s, calculate the moment of inertia of the system about the z axis. Correct answer: 38.8632 N. 007 (part 3 of 3) 10.0 points Find the force in the cord supporting the larger mass. Correct answer: 46.6592 N. 002 (part 2 of 2) 10.0 points Find the rotational energy of the system. Correct answer: 9337.5 J. Torque on a Grinding Wheel 003 (part 1 of 2) 10.0 points A grinding wheel is in the form of a uniform solid disk of radius 5.38 cm and mass 2.28 kg. It starts from rest and accelerates uniformly under the action of the constant torque of 0.75 N · m that the motor exerts on the wheel. How long does the wheel take to reach its final speed of 1790 rev/min? 004 (part 2 of 2) 10.0 points Through how many revolutions does it turn Holt SF 08Rev 71 008 10.0 points The figure shows a system of four m = 3.6 kg point masses that rotates at an angular speed of 6 rev/s . The masses are connected by light, flexible spokes of 4.6 m and 7.2 m length that can be elongated or shortened. Sample HW07 - PHYS 21800 2 force on the bottom of the boom. y m Correct answer: 2305.54 N. 7.2 m 6 rev/s m m x 011 (part 3 of 3) 10.0 points Find the vertical component of the reaction force on the bottom of the boom. Correct answer: 4069.91 N. 4.6 m 6 rev/s m = 3.6 kg What is the new angular speed if each of the spokes to shortened by 15% of their original length? An effect similar to this ocurred in the early stages of the formation of our galaxy. As the massive cloud of gas and dust contracted, an initially small rotation increased with time. Serway CP 08 56 012 (part 1 of 2) 10.0 points A 0.1 kg meter stick is supported at its 40 cm mark by a string attached to the ceiling. A 0.597 kg object hangs vertically from the 5.66 cm mark. A second mass is attached at another mark to keep it horizontal and in rotational and translational equilibrium. If the tension in the string attached to the ceiling is 18.6 N, find the value of the second mass. The acceleration due to gravity is 9.8 m/s2 . Correct answer: 266.667 rev/s. Holt SF 08Rev 22 009 (part 1 of 3) 10.0 points A 1261 N uniform boom of length ! is supported by a cable, as shown. The boom is pivoted at the bottom, the cable is attached 3 a distance ! from the pivot, and a 3884 N 4 weight hangs from the boom’s top. FT 25◦ 3884 N 65◦ Find the force FT applied by the supporting cable. Correct answer: 2543.88 N. 010 (part 2 of 3) 10.0 points Find the horizontal component of the reaction 013 (part 2 of 2) 10.0 points Find the mark at which the second mass is attached. Your answer must be in cm.