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Katena32 [7]
3 years ago
13

An escalator handles a steady load of 26 people per minute in elevating them from the first to the second floor through a vertic

al rise of 27.5 ft. The average person weighs 124 lb. If the motor which drives the unit delivers 3.8 hp, calculate the mechanical efficiency e of the system.
Engineering
1 answer:
photoshop1234 [79]3 years ago
3 0

Answer:

\eta = 70.711\,\%

Explanation:

The power needed to make the escalator working is obtained by means of the Work-Energy Theorem:

\dot W  = \dot U_{g}

\dot W = \dot n \cdot m_{p}\cdot g \cdot \Delta y

\dot W = \left(26\,\frac{persons}{min}\right)\cdot (124\,lbm)\cdot \left(32.174\,\frac{ft}{s^{2}}\right)\cdot \left(\frac{1\,lbf}{32.174\,\frac{lbm\cdot ft}{s^{2}} } \right)\cdot (27.5\,ft)

\dot W = 88660\,\frac{lbf\cdot ft}{min}\,\left(2.687\,hp\right)

The mechanical efficiency of the escalator is:

\eta = \frac{2.687\,hp}{3.8\,hp}\times 100\,\%

\eta = 70.711\,\%

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Bessy's calf weighed 99.19 pounds when calved on March 7th. Her calf gained an average of 1.85 pounds per day for 266 days. What
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Answer:

591.3

Explanation:

99.19 + (1.85 × 266) = 591.29

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4 0
3 years ago
Your program must output each student’s name in the form: last name followed by a comma, followed by a space, followed by the fi
Reptile [31]

Answer:

#include <iostream>

#include <string>

#include <fstream>

using namespace std;

char getStudentGrade(int testScore);

//Declare constant max students in file 10

const int maxStudents = 10;

struct StudentType

{

  string studentFName;

  string studentLName;

  int testScore;

  char grade;

};

void readStudentData(StudentType students[]){

  int i = 0;

 

  ifstream infile;

  infile.open("inputStudentData.txt");

 

 

  while (!infile.eof())

  {

   infile >> students[i].studentFName;

   infile >> students[i].studentLName;

   infile >> students[i].testScore;

   students[i].grade = getStudentGrade(students[i].testScore);

      i++;

  }

}

char getStudentGrade(int testScore){

  char grade;

  if(testScore >= 80) {

      grade = 'A';      

  }

  else if(testScore >= 60) {

      grade = 'B';

  }

  else if(testScore >= 50) {

      grade = 'C';  

  }

  else if(testScore >= 40) {

      grade = 'D';      

  }

  else {

      grade = 'F';  

  }

  return grade;

}

int main()

{

 

  StudentType students[10];

 

  readStudentData(students);

 

  for(int i=0;i<maxStudents;i++) {

      students[i].grade = getStudentGrade(students[i].testScore);

  }

 

  for(int i=0; i<maxStudents; i++){    

      cout << students[i].studentLName <<", " << students[i].studentFName << " " << students[i].grade << endl;

  }

  ofstream outputFile;

  outputFile.open ("outputStudentData.txt");

 

  for(int i=0; i<maxStudents; i++){    

      outputFile << students[i].studentLName <<", " << students[i].studentFName << " " << students[i].grade << endl;

  }

  outputFile.close();

  return 0;

}

3 0
3 years ago
According to one government agency, bad housekeeping is estimated to cause what percentage
muminat
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8 0
3 years ago
The pump of a water distribution system is powered by a 6-kW electric motor whose efficiency is 95 percent. The water flow rate
Sonja [21]

Answer:

a) Mechanical efficiency (\varepsilon)=63.15%  b) Temperature rise= 0.028ºC

Explanation:

For the item a) you have to define the mechanical power introduced (Wmec) to the system and the power transferred to the water (Pw).

The power input (electric motor) is equal to the motor power multiplied by the efficiency. Thus, Wmec=0.95*6kW=5.7 kW.

Then, the power transferred (Pw) to the fluid is equal to the flow rate (Q) multiplied by the pressure jump \Delta P. So P_W = Q*\Delta P=0.018m^3/s * 200x10^3 Pa=3600W.

The efficiency is defined as the ratio between the output energy and the input energy. Then, the mechanical efficiency is \varepsilon=3.6kW/5.7kW=0.6315=63.15\%

For the b) item you have to consider that the inefficiency goes to the fluid as heat. So it is necessary to use the equation of the heat capacity but in a "flux" way. Calling <em>H</em> to the heat transfered to the fluid, the specif heat of the water and \rho the density of the water:

[tex]H=(5.7-3.6) kW=\rho*Q*c*\Delta T=1000kg/m^3*0.018m^3/s*4186J/(kg \ºC)*\Delta T[/tex]

Finally, the temperature rise is:

\Delta T=2100/75348 \ºC=0.028 \ºC

7 0
3 years ago
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