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MCD 4140 Computing for Engineers

Self Study Exercise 7

Note: Tasks below can use for both hand calculation practice and programming practice.

Note: You might want to use extra sheet for hand calculation practice.

Task 1

Find  the  best  fit  line  for  the  data  given  below  by  performing  linear regression. Calculate the r2 value.

x

y

0.6

5.282

1.36

5

2.12

6.5

2.88

7.2656

3.64

7.2

4.4

8.588

5.16

10

5.92

11

Task 2

Find the best fit line for the data given below by performing non-linear regression using the Exponential Model. Calculate the r2 value. (Note: You can  also try to solve this  problem  using  Power  Model and  Saturation- Growth-Rate model)

X

y

0.6

5.282

3.64

7.2

6.68

10.5716

9.72

13.2164

12.76

17

15.8

22

18.84

29

Task 3

Use least-squares regression to fit a straight line to

x

0

2

4

6

9

11

12

15

17

19

y

5

6

7

6

9

8

7

10

12

12

Along with the slope and intercept, compute the standard error of the estimate and the correlation coefficient. Plot the data and the regression line. Then repeat the problem, but regress x versus y—that is, switch the variables. Interpret your results.

Task 4

You measure the voltage drop V across a resistor for a number of different values of current !. The results are

i

0.25

0.75

1.25

1.5

2.0

v

-0.45

-0.6

0.7

1.88

6.0

Use first- through fourth-order polynomial interpolation to estimate the voltage drop for ! = 1.15. Interpret your results.

Task 5

The specific volume of a superheated steam is listed in steam tables for various temperatures. For example, at a pressure of 3000 lb/in2, absolute:

T, °F

700

720

740

760

780

v, fts/1hz

0.0977

0.12184

0.14060

0.15509

0.16643

Determine v at T = 750 °F.

Task 6

The following data was gathered to determine the relationship between the pressure and the temperature of 1 kg of nitrogen with a fixed volume of 10 m3 .

T [K]

253.15

273.15

293.15

313.15

323.15

343.15

373.15

393.15

p [N/m2]

7500

8104

8700

9300

9620

10200

11200

11700

Employ the ideal gas law pV = nRT to estimate the constant R on the basis  of this data.  Note that the temperature T  must  be  expressed  in kelvins  [K]  (0°C  =  273.15  K).  The  number  of  moles  [mol]  of  nitrogen molecules (N2) is n = (1 kg) /(0.028 kg/mol). (The accepted value for R is 8.31447 N.m/(mol.K). Refer to website http://physics.nist.gov/cuu.)

Task 7

On average the surface area A of human beings is related to height H and weight W . Measurements on a number of individuals of height 1.80 m and different weights [kg-wt] give values of surface area [m2] in the following table.

W [kg-wt]

70

75

77

80

82

84

87

90

A [m2]

2.10

2.12

2.15

2.20

2.22

2.23

2.26

2.30

Show that a power law A = aWb fits these data reasonably well. Evaluate

the constants a and b , and predict what the surface area is for a person of height 1.80 m and weight 95 kg-wt.

Task 8

Fit a parabola to the data from table below. Determine the r2 for the fit and

comment on the efficacy of the result.

v, [m/s]

10

20

30

40

50

60

70

80

F, [N]

25

70

380

550

610

1220

830

1450