277_Dynamics 11ed Manual

277_Dynamics 11ed Manual - The load of weight W is hoisted...

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Engineering Mechanics - Dynamics Chapter 14 Problem 14-57 The block has mass M and rests on a surface for which the coefficients of static and kinetic friction are μ s and k respectively. If a force F = kt 2 is applied to the cable, determine the power developed by the force at t = t 2 . Hint: First determine the time needed for the force to cause motion. Given: M 150 kg = k 60 N s 2 = s 0.5 = g 9.81 m s 2 = k 0.4 = t 2 5s = Solution: 2 F 2 kt 1 2 = s Mg = t 1 s Mg 2 k = t 1 2.476 s = 2 kt 2 k Mg Ma = M t v d d = v 2 t 1 t 2 t 2 kt 2 M k g d = v 2 19.381 m s = P 2 kt 2 2 v 2 = P 58.144 kW = Problem 14-58
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Unformatted text preview: The load of weight W is hoisted by the pulley system and motor M . If the crate starts from rest and by constant acceleration attains a speed v after rising a distance s = s 1 , determine the power that must be supplied to the motor at this instant. The motor has an efficiency . Neglect the mass of the pulleys and cable. Given: W 50 lbf = 0.76 = v 15 ft s = g 32.2 ft s 2 = s 1 6 ft = 275...
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