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mina [271]
3 years ago
7

Define the stress and strength? A material has yield strength 100 kpsi. A cantilever beam has length 10 in and a load of 100 Lbf

is applied at the free end. The beam cross section is rectangular 2""x5’. Is the beam design acceptable or not for a factor of safety 2?
Engineering
1 answer:
Firlakuza [10]3 years ago
4 0

Answer:

Stress is a force that acts on a unit area of a material. The strength of a material is how much stress it can bear without permanently deforming or breaking.

Is the beam design acceptable for a SF of 2? YES

Explanation:

Your factor of safety is 2, this means your stress allowed is:

  • σall = YS/FS = 100kpsi/2 = 50kpsi

Where:

  • σall => Stress allowed
  • YS => Yield Strength
  • FS => Factor of safety

Now we are going to calculate the shear stress and bending stresses of the proposed scenario. If the calculated stresses are less than the allowed stress, that means the design is adequate for a factor of safety of 2.

First off we calculate the reaction force on your beam. And for this you do sum of forces in the Y direction and equal to 0 because your system is in equilibrium:

  1. ΣFy = 0
  2. -100 + Ry = 0     thus,
  3. Ry = 100 lbf

Knowing this reaction force you can already calculate the shear stress on the cantilever beam:

  1. τ = F/A
  2. τ = 100lbf/(2in*5in)
  3. τ = 10 psi

Now, you do a sum of moments at the fixed end of your cantilever beam, so you can cancel off any bending moment associated with the reaction forces on the fixed end, and again equal to 0 because your system is in equilibrium.

  1. ΣM = 0
  2. -100lbf*10in + M = 0
  3. M = 1000 lbf-in

Knowing the maximum bending moment you can now calculate your bending stress as follows:

  • σ = M*c/Ix

Where:

  • σ => Bending Stress
  • M => Bending Moment
  • c => Distance from the centroid of your beam geometry to the outermost fiber.
  • Ix => Second moment area of inertia

Out of the 3 values needed, we already know M. But we still need to figure out c and Ix. Getting c is very straight forward, since you have a rectangle with base (b) 2 and height (h) 5, you know the centroid is right at the center of the rectangle, meaning that the distance from the centroid to the outermost fibre would be 5in/2=2.5in

To calculate the moment of Inertia, you need to use the formula for the second moment of Inertia of a rectangle and knowing that you will use Ix since you are bending over the x axis:

  • Ix = (b*h^3)/12 = (2in*5in^3)/12 = 20.83 in4

Now you can use this numbers in your bending stress formula:

  1. σ = M*c/Ix
  2. σ = 1000 lbf-in * 2.5in / 20.83 in4
  3. σ = 120 psi

The shear stress is 10psi and the bending stress is 120psi, this means you are way below the stress allowed which is 50,000 psi, thus the beam design is acceptable. You could actually use a different geometry to optimize your design.

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Elena L [17]

Answer:

6,3,2,5,1,4 because they jst are

Explanation:

3 0
3 years ago
Biologists use a sequence of letters A, C, T, and G to model a genome. A gene isa substring of a genome that starts after a trip
kogti [31]

Answer:

You did not mention the programming language for implementation so i am writing a JAVA code.

import java.util.Scanner; // to get input from user

public class Genome{

public static void main(String[] args) { //start of main() function body

Scanner input = new Scanner(System.in); //creates Scanner object

System.out.print("Enter a genome string: ");

//prompts user to enter a genome string

String genome = input.nextLine();

//reads the input genome string and stores it into genome variable

boolean gene_found = false;

//variable gene_found of boolean type that has two value true or false

int startGene = 0; // stores starting of the gene string

for (int i = 0; i < genome.length() - 2; i++) {

//loop moves through genome string until the third last gene character

String triplet = genome.substring(i, i + 3);

//stores the triplet of genome substring

if (triplet.equals("ATG")) {

//if value in triplet is equal to ATG

startGene = i + 3;

//3 is added to i-th position of the genome string

}

else if (((triplet.equals("TAG")) || (triplet.equals("TAA")) || (triplet.equals("TGA"))) &&(startGene != 0))

//checks if the genome ends with one the given triplets TAG TAA and TGA

{ String gene = genome.substring(startGene, i);

gene stores substring of genome string from startGene to the position i

if (gene.length() % 3 == 0)

//if the the mod of gene length is 0 then the gene is found

{gene_found = true;

System.out.println(gene); //returns the found gene

startGene = 0;} } }

if (!gene_found) //if gene is not found returns the message below

System.out.println("no gene is found"); }  }

Explanation:

This program first asks user to enter a genome string.

The loop starts from the first character of the entered string and this loop continues to execute until the value of i is 2 less than the genome input string length.

triplet variable stores first 3 characters of the genome string in first iteration and then moves through the string taking 3 characters each. This is done by dividing genome string to substring of 3 characters.

If condition checks if the 3 characters of genome string matches ATG using equals() function. If it is true this means start of genome is reached and these triplets are stored in startGene.

Else condition checks the end of the genome as the genome ends before one of TAG, TAA or TGA triplets. So this is checked here.

gene variable holds the triplet value stored in startGene and the value stored in index position i which means it holds the start of the genome till the end of the genome sequence. The end which is pointed by i variable is 2 less than the genome length and it is stored in gene variable.

After the loop ends the substring stored in gene variable is checked for a valid genome sequence by mod operator. If the length of the value stored in gene variable mod 0 is equal to 0 this means genome sequence is found and this string sequence stored in gene is displayed else the no gene is found message is displayed on output screen.

7 0
3 years ago
Develop rough sketches of ideas bridge ​
irga5000 [103]

Answer:

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Explanation:

3 0
3 years ago
Interpret the Blame responsibility and causation in your own words in the light of Columbia Accident.
Licemer1 [7]

Answer:

Proposed Improvements and Generic Lessons

Within 2 h of losing the signal from the returning spacecraft, NASA’s Administrator established the Columbia Accident Investigation Board (CAIB) to uncover the conditions that had produced the disaster and to draw inferences that would help the US space program to emerge stronger than before (CAIB, 2003). Seven months later, the CAIB released a detailed report that included its recommendations (Starbuck and Farjoun, 2005).

The CAIB (2003) report attempted to seek answers to the following four crucial questions:

1.

Why did NASA continue to launch spacecraft despite many years of known foam debris problems?

2.

Why did NASA managers conclude, despite the concerns of their engineers, that the foam debris strike was not a threat to the safety of the mission?

3.

How could NASA have forgotten the lessons of Challenger?

4.

What should NASA do to minimize the likelihood of such accidents in the future?

Although the CAIB’s comprehensive report raised important questions and offered answers to some of them, it also left many major questions unanswered (Starbuck and Farjoun, 2005).

1.

Why did NASA consistently ignore the recommendations of several review committees that called for changes in safety organization and practices?

2.

Did managerial actions and reorganization efforts that took place after the Challenger disaster contribute, both directly and indirectly, to the Columbia disaster?

3.

Why did NASA’s leadership fail to secure more stable funding and to shield NASA’s operations from external pressures?

By examining, with respect to the Columbia disaster, the case of NASA as an organization, one can try to extract generalizations that could be useful for other organizations, especially those engaged in high-risk activities—such as nuclear power plants, oil and gas, hospitals, airlines, armies, and pharmaceutical companies—and such generic principles may also be salutary for any kind of organization.

The CAIB (2003) report recommended developing a plan to inspect the condition of all RCC systems, the investigation having found the existing inspection techniques to be inadequate. RCC panels are installed on parts of the shuttle, including the wing leading edges and nose cap, to protect against the excessive temperatures of reentry. They also recommended that taking images of each shuttle while in orbit should be standard procedure as well as upgrading the imaging system to provide three angles of view of the shuttle, from liftoff to at least SRB separation. “The existing camera sites suffer from a variety of readiness, obsolescence, and urban encroachment problems.” The board offered this suggestion because NASA had had no images of the Columbia shuttle clear enough to determine the extent of the damage to the wing. They also recommended conducting inspections of the TPS, including tiles and RCC panels, and developing action plans for repairing the system. The report included 29 recommendations, 15 of which the board specified must be completed before the shuttle returned to flight status, and also made 27 “observations” (CAIB, 2005).

7 0
3 years ago
A gas stream contains 18.0 mole% hexane and the remainder nitrogen. The stream flows to a condenser, where its temperature is re
Anna [14]

Answer:

A. 72.34mol/min

B. 76.0%

Explanation:

A.

We start by converting to molar flow rate. Using density and molecular weight of hexane

= 1.59L/min x 0.659g/cm³ x 1000cm³/L x 1/86.17

= 988.5/86.17

= 11.47mol/min

n1 = n2+n3

n1 = n2 + 11.47mol/min

We have a balance on hexane

n1y1C6H14 = n2y2C6H14 + n3y3C6H14

n1(0.18) = n2(0.05) + 11.47(1.00)

To get n2

(n2+11.47mol/min)0.18 = n2(0.05) + 11.47mol/min(1.00)

0.18n2 + 2.0646 = 0.05n2 + 11.47mol/min

0.18n2-0.05n2 = 11.47-2.0646

= 0.13n2 = 9.4054

n2 = 9.4054/0.13

n2 = 72.34 mol/min

This value is the flow rate of gas that is leaving the system.

B.

n1 = n2 + 11.47mol/min

72.34mol/min + 11.47mol/min

= 83.81 mol/min

Amount of hexane entering condenser

0.18(83.81)

= 15.1 mol/min

Then the percentage condensed =

11.47/15.1

= 7.59

~7.6

7.6x100

= 76.0%

Therefore the answers are a.) 72.34mol/min b.) 76.0%

Please refer to the attachment .

4 0
3 years ago
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