41
Chapter 7: Length and Length-Related Variables in Engineering
7.22 A machinist in an engineering machine shop has ordered a sheet of plastic with
dimensions of 10 ft ×12 ft ×1 in. width, length, and thickness, respectively. Can
the machinist get the sheet of plastic inside the machine shop provided that the
door dimensions are 6 ft ×8 ft? Give the maximum dimensions of a sheet that can
be moved inside the shop and explain how.
SOLUTION
6 ft
B
42
7.37 Calculate the second moment of area of a 4-in-diameter shaft about the x-x and y-
y axes, as shown.
7.38 Calculate the second moment of area for a 2 × 6 piece of umber about the x-x
and y-y axes, as shown. Visit a hardware store and measure the actual dimensions
of a typical 2 × 6 piece of lumber.
SOLUTION
4
3
3in 55.1in 5.1in 5.5
12
1
Wh
12
1
xx
I
SOLUTION
7.40 How many 5-in-diameter, ¼-in thick disks can be fitted into a 4 ft-long, 5¼-
diameter cylindrical container?
7.41 In U.S., the fuel consumption of an automobile is expressed in X miles per gallon.
Obtain a single factor that could be used to convert the X miles per gallon to km
per liter.
7.42 Calculate the arc length S1 in the accompanying figure. R2 = 8 cm, R1 = 5 cm,
S2 = 6.28 cm
SOLUTION
8
5
R
R
1
2
1
7.43 A 10-cm-long rectangular bar (when subjected to a tensile load) deforms by 0.1
mm. Calculate the normal strain.
SOLUTION
L
7.44 Calculate the volume of material used in making 100 ft of 4-in. type K, copper
tubing.
4
7.45 Calculate the volume of material used in making 100 ft of 4- in. type L, copper
tubing.
4
7.46 Calculate the volume of material used in making 100 ft of 4-in. type M, copper
tubing.
4
7.47 By what factor do you increase the resistance to bending (about x-x axis) if you
were to use W18 × 76 beam over W8 × 31?
7.48 By what factor do you increase the resistance to bending (about y-y axis) if you
were to use W18 × 76 beam over W8 × 31?
7.49 Estimate the frontal area (excluding the display panel) of the cell phone shown in
the accompanying figure.
SOLUTION
7.50 Estimate the frontal area of the car shown in the accompanying figure.