Pancake collapse of a tall building. In the section of a tall building shown in Fig. 9-71 a , the infrastructure of any given floor K must support the weight W of all higher floors. Normally the infrastructure is constructed with a safety factor s so that it can withstand an even greater downward force of sW . If, however, the support columns between K and L suddenly collapse and allow the higher floors to free-fall together onto floor K (Fig. 9-71 b ), the force in the collision can exceed sW and, after a brief pause, cause K to collapse onto floor J, which collapses on floor I, and so on until the ground is reached. Assume that the floors are separated by d = 4.0 m and have the same mass. Also assume that when the floors above K free-fall onto K, the collision lasts 1.5 ms. Under these simplified conditions, what value must the safety factor 5 exceed to prevent pancake collapse of the building? Figure 9-71 Problem 82.
Pancake collapse of a tall building. In the section of a tall building shown in Fig. 9-71 a , the infrastructure of any given floor K must support the weight W of all higher floors. Normally the infrastructure is constructed with a safety factor s so that it can withstand an even greater downward force of sW . If, however, the support columns between K and L suddenly collapse and allow the higher floors to free-fall together onto floor K (Fig. 9-71 b ), the force in the collision can exceed sW and, after a brief pause, cause K to collapse onto floor J, which collapses on floor I, and so on until the ground is reached. Assume that the floors are separated by d = 4.0 m and have the same mass. Also assume that when the floors above K free-fall onto K, the collision lasts 1.5 ms. Under these simplified conditions, what value must the safety factor 5 exceed to prevent pancake collapse of the building? Figure 9-71 Problem 82.
Pancake collapse of a tall building. In the section of a tall building shown in Fig. 9-71a, the infrastructure of any given floor K must support the weight W of all higher floors. Normally the infrastructure is constructed with a safety factor s so that it can withstand an even greater downward force of sW. If, however, the support columns between K and L suddenly collapse and allow the higher floors to free-fall together onto floor K (Fig. 9-71 b), the force in the collision can exceed sW and, after a brief pause, cause K to collapse onto floor J, which collapses on floor I, and so on until the ground is reached. Assume that the floors are separated by d = 4.0 m and have the same mass. Also assume that when the floors above K free-fall onto K, the collision lasts 1.5 ms. Under these simplified conditions, what value must the safety factor 5 exceed to prevent pancake collapse of the building?
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Question 4 of 6
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The uniform 25-m pole has a mass of 120 kg and is supported by its smooth ends against the vertical walls and by the tension T in the
vertical cable. Compute the magnitudes of the reactions at A and B.
B
T
17 m
7
8 m
A
20 m
8:27
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18/06
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a
8-53.. A lantern of weight W is suspended at the end
horizontal bar of weight w and length L that is supported
by a cable that makes an angle with the side of a
vertical wall. Assume the weight of the bar is at its
center.
(a) Derive an equation for the tension in the cable.
(b) Calculate the tension in the cable for a bar of weight
28 N and length 1.5 m, plus a lantern of weight 85 N,
and the cable making a 37° angle to the vertical.
40²
D
In the figure a 51 kg rock climber is in a lie-back climb along a fissure, with hands pulling on one side of the fissure and feet pressed
against the opposite side. The fissure has width w = 0.30 m, and the center of mass of the climber is a horizontal distance d = 0.30 m
from the fissure. The coefficient of static friction between hands and rock is µ₁ = 0.40, and between boots and rock it is µ2 = 1.10. The
climber adjusts the vertical distance h between hands and feet until the (identical) pull by the hands and push by the feet is the least
that keeps him from slipping down the fissure. (He is on the verge of sliding.)
(a) What is the least horizontal pull by the hands and push by the feet that will keep the climber stable? (b) What is the value of h?
(a) Number
Units
(b) Number
Units
com
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