Question

An elevator is designed to travel a height of 4.5 meters when loaded and will have a maximum gross weight of 250 kg. A coil spring is provided below to absorb shock in the event that the elevator should fall freely because of sudden breakage of the wire rope carrying it. If the coil spring is deflected to 50 cm when the elevator accidentally falls and hits the spring from its maximum height of travel, determine the following: (Use a spring index of 9.5 and assume the maximum induced stress and shear modulus of elasticity to be 4500 kg/cm² and 900500 kg/cm², respectively.) A. Wire diameter A) 8.6 cm B) 5.56 cm C) 7.32 cm D) 4.4 cm B. Mean coil diameter A) 50.68 cm B) 51.42 cm C) 52.82 cm D) 54.34 cm C. Number of active coils A) 7.3 B) 8.3 C) 6.2 D) 8.8

          An elevator is designed to travel a height of 4.5 meters when loaded and will have a maximum gross weight of 250 kg. A coil spring is provided below to absorb shock in the event that the elevator should fall freely because of sudden breakage of the wire rope carrying it. If the coil spring is deflected to 50 cm when the elevator accidentally falls and hits the spring from its maximum height of travel, determine the following: (Use a spring index of 9.5 and assume the maximum induced stress and shear modulus of elasticity to be 4500 kg/cm² and 900500 kg/cm², respectively.) 

A. Wire diameter 
   A) 8.6 cm 
   B) 5.56 cm 
   C) 7.32 cm 
   D) 4.4 cm 

B. Mean coil diameter 
   A) 50.68 cm 
   B) 51.42 cm 
   C) 52.82 cm 
   D) 54.34 cm 

C. Number of active coils 
   A) 7.3 
   B) 8.3 
   C) 6.2 
   D) 8.8
        
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Added by Julio D.

University Physics with Modern Physics
University Physics with Modern Physics
Hugh D. Young 14th Edition
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An elevator is designed to travel a height of 4.5 meters when loaded and will have a maximum gross weight of 250 kg. A coil spring is provided below to absorb shock in the event that the elevator should fall freely because of sudden breakage of the wire rope carrying it. If the coil spring is deflected to 50 cm when the elevator accidentally falls and hits the spring from its maximum height of travel, determine the following: (Use a spring index of 9.5 and assume the maximum induced stress and shear modulus of elasticity to be 4500 kg/cm² and 900500 kg/cm², respectively.) A. Wire diameter A) 8.6 cm B) 5.56 cm C) 7.32 cm D) 4.4 cm B. Mean coil diameter A) 50.68 cm B) 51.42 cm C) 52.82 cm D) 54.34 cm C. Number of active coils A) 7.3 B) 8.3 C) 6.2 D) 8.8
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Transcript

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00:01 In this question we've been told that an elevator with a mass of 1 ,500 kg is supported by a steel cable.
00:07 The cable breaks when the bottom of the elevator is 10 meter above a spring, which has a force constant of 10 ,000 newton per meter.
00:16 So in the first part of the question, we need to find the speed of the elevator when it first contacts the spring.
00:22 So we need to find the speed.
00:26 So we know that it is 10 meter above the spring.
00:30 So we know the distance we know that it will be under the force of gravity so we are going to use a formula 2 as equals to v square minus u square so v is the initial v is the final speed and u is the initial speed so we know that in this case the initial speed is going to be 0 so 2 as equals to v square and v equals to under root 2 s so this is going to be under root 2 multiplied by acceleration in this case will be gravitational acceleration which is 9 .8.
01:13 1 multiplied by the distance which is s 10 meters.
01:19 So v is going to be 14 meter per second.
01:26 So this is the velocity of the elevator when it first contact the spring.
01:32 And this is the answer for part a.
01:33 In part b, we need to find out by what distance is the spring compressed when the force of the spring is equal to the force of gravity...
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