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A half-cylinder with mass m and radius r is released from rest in the position shown. Knowing that the half-cylinder rolls without sliding, determine (a) its angular velocity after it has rolled through 900, (b) the reaction at the horizontal surface at the same instant. (Hint: Note that
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Vector Mechanics For Engineers
- A slender 9-lb rod can rotate in a vertical plane about a pivot at B. A spring of constant k = 30 lb/ft and of unstretched length 6 in. is attached to the rod as shown. Knowing that the rod is released from rest in the position shown, determine its angular velocity after it has rotated through 90°.arrow_forwardThe rotor of an electric motor has an angular velocity of 4500 rpm when the load and power are cut off. The 75-kg rotor, which has a centroidal radius of gyration of 200 mm, then coasts to rest. Knowing that kinetic friction results in a couple of magnitude 4.5 Nm. exerted on the rotor, determine the number of revolutions that the rotor executes before coming to rest.arrow_forwardThe 80-mm-radius gear shown has a mass of 5 kg and a centroidal radius of gyration of 60 mm. The 4-kg rod AB is attached to the center of the gear and to a pin at B that slides freely in a vertical slot. Knowing that the system is released from rest when 0 = 60°, determine the velocity of the center of the gear when 0 = 20°.arrow_forward
- The rotor of an electric motor has an angular velocity of 3600 rpm when the load and power are cut off. The 110-lb rotor, which has a centroidal radius of gyration of 9 in., then coasts to rest. Knowing that the kinetic friction of the rotor produces a couple with a magnitude of 2.5 1b.ft determine the number of revolutions that the rotor executes before coming to rest.arrow_forwardA collar with a mass of 1 kg is rigidly attached to a slender rod AB of mass 3 kg and length L = 600 mm. The rod is released from rest in the position shown. Determine the distance d for which the angular velocity of the rod is maximum after it has rotated through 90°.arrow_forwardThe space capsule has no angular velocity when the jet at A is activated for 1 s in a direction parallel to the axis. Knowing that the capsule has a mass of 1000 kg, that its radii of gyration are Kz=Ky =1.00m and Kz=1.25m A produces a thrust of 50 N, determine the axis of precession and the rates of precession and spin after the jet has stopped.arrow_forward
- Disk A has a mass mA = 4 kg, a radius rA = 300 mm, and an initial angular velocity ω0 = 300 rpm clockwise. Disk B has a mass mB = 1.6 kg, a radius rB = 180 mm, and is at rest when it is brought into contact with disk A. Knowing that µk = 0.35 between the disks and neglecting bearing friction, determine (a) the angular acceleration of each disk, (b) the reaction at the support C.arrow_forwardA wheel of radius r and centroidal radius of gyration k is released from rest on the incline shown at time t = 0. Assuming that the wheel rolls without sliding, determine (a) the velocity of its center at time t, (b) the coefficient of static friction required to prevent slipping.arrow_forwardThe 30-kg reel is mounted on a 20 kg cart. The reel is free to rotate about the axle O. The radius of gyration, kO, about the mass center, O, is 250 mm and a cable is wrapped around the inner hub of the wheel. The mass of the wheels on the cart and the mass of the cable may be neglected. The system is at rest when a force, P, of 50 N is applied to the end of the cable. a) Determine the velocity of the cart after 4 seconds m/s b) determine the angular velocity of the reel, in rad/s. [Correct answers are a) 4.0 m/s b) 16 rad/sarrow_forward
- A 18-kg rear hatch of a vehicle opens as shown in the figure and can be modeled as a uniform 0.6-m long slender rod. Knowing that the tailgate is released from rest in the position shown in the figure, determine the angular velocity of the tailgate as it impacts the car body.arrow_forwardThe 30-kg uniform disk A and the bar BC are at rest and the 5-kg uniform disk D has an initial angular velocity of w1 with a magnitude of 440 rpm when the compressed spring is released and disk D contacts disk contacts disk A. The system rotates freely about the vertical spindle BE. After a period of slippage, disk D rolls without slipping. Knowing that the magnitude of the final angular velocity of disk D is 176 rpm, determine the final angular velocities of bar BC and disk A. Neglect the mass of bar BC.arrow_forwardA bullet weighing 0.08 lb is fired with a horizontal velocity of 1800 ft/s into the lower end of a slender 15-lb bar of length L = 30 in. Knowing that h = 12 in. and that the bar is initially at rest, determine (a) the angular velocity of the bar immediately after the bullet becomes embedded, (b ) the impulsive reaction at C , assuming that the bullet becomes embedded in 0.001 s.arrow_forward
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