Engineering Fundamentals: An Introduction to Engineering, 4th ed.c

Problems 631

formula used to measure the acceleration due to

gravity is

where gis acceleration due to gravity ( m/s

2

), Lis the

length of pendulum, and Tis the period of oscillation of

the pendulum (the time that it takes the pendulum to

complete one cycle). For a pendulum of 2 m long, create

a graph that could be used for locations between an alti-

tude of 0 and 2000 m, and shows gas a function of T.

18.30.The mass moment of inertia Iof a disk is given by

where mis the mass of the disk and ris the radius. Cre-

ate a graph that shows Ias a function of rfor a steel

disk with a density of 7800 kg /m

3

. Vary the rvalue
from 10 cm to 25 cm.
18.31.Use the linear interpolation method discussed in
Section 18.2 to estimate the density of air at an alti-
tude 4150 m.
18.32.For the cooling of steel plates discussed in Section 18.4
(Figure 18.12) using linear interpolation, estimate the
temperature of the plate at time equal to 1 hr, from
the temperature data at 0.8 hr and 1.2 hour. Compare
the estimated temperature value to the actual value of
308 °C. What is the percentage of error?
18.33.For the stopping sight distance problem of Figure 18.7,
estimate the stopping distance for speed of 27 mph,
using the 25 mph and 30 mph data. Compare the esti-
mated stopping distance value to the actual value from
Equation (18.7). What is the percentage of error?

I

1

2

mr

2

g

4 p

2

L

T

2

18.34.The variation of air density at the standard pressure as

a function of temperature is given in the accompanying

table. Use linear interpolation to estimate the air density

at 27 °C and 33 °C.

Air

Altitude Temperature Speed of

(m) (K) Sound (m/s)

500 284.9 338

1000 281.7 336

2000 275.2 332

5000 255.7 320

10,000 223.3 299

15,000 216.7 295

20,000 216.7 295

Electricity Generation by Fuel, 1980–2030 (billion kilowatt-hours)—Data from U.S. Department of Energy

Year Coal Petroleum Natural Gas Nuclear Renewable /Other

1980 1161.562 245.9942 346.2399 251.1156 284.6883 actual values

1990 1594.011 126.6211 372.7652 576.8617 357.2381 actual values

2000 1966.265 111.221 601.0382 753.8929 356.4786 actual values

2005 2040.913 115.4264 751.8189 774.0726 375.8663 actual values

2010 2217.555 104.8182 773.8234 808.6948 475.7432 projected values

2020 2504.786 106.6799 1102.762 870.698 515.1523 projected values

2030 3380.674 114.6741 992.7706 870.5909 559.1335 projected values

Temperature (°C) Air Density (kg /m^3 )

0 1.292

5 1.269

10 1.247

15 1.225

20 1.204

25 1.184

30 1.164

35 1.146

18.35.The air temperature and speed of sound for the U.S.

standard atmosphere is given in the accompanying

table. Using linear interpolation, estimate the air tem-

peratures and the corresponding speeds of sound at

altitudes of 1700 m and 11,000 m.

For Problems 18.36 through 18.42 use the data from the accompanying table shown below.

Source:Data from U.S. Department of Energy

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