# hw13 - Homework No 13 Work and power in rotation Y&F 10.32...

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Homework No. 13 Work and power in rotation Y&F 10.32 Ans : (a) 46.2 rad/s 2 (b) 53.9 rad/s (c) 61.3 kJ (d) 52.6 kW (e) 105 kW Note : Treat the propeller as a slender rod pivoted at its center. O R = 0.4 m L = 0.6 m Energy equation including rigid body rotation CHANG 1 An 8 Kg slender rod and a small 4 Kg sphere are mounted on a 15 Kg disk. The assembly is released from rest at the horizontal position shown. Find the angular velocity of the assembly when it rotates 90° down to the vertical position. Ans : 5.11 rad/s CHANG 2 The 10 Kg block is attached to a spring (k = 100 N/m) and a cord that wraps around the pulley as shown. The block slides on the tabletop ( μ = 0.4) as a constant torque τ = 25 Nm is applied to turn the pulley from rest. The pulley (radius R = 0.1 m, moment of inertia I = 0.24 Kgm2) is pivoted at the center and the spring is initially unstretched. Fin k d the

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