Modern Engineering Thermodynamics

Problems 27
Problems (* indicates problems in SI units)
1.* Using the problem solving technique described at the beginning
of the chapter, work out your answer to the following question:
A fresh egg is released by an ancient pterodactyl flying
horizontally at 10. m/s at an altitude of 1500 km (Figure 1.20).
If it takes 15 s for the egg to hatch, will it hatch before it hits
the ground?
10. m/s
Egg
1500 km
FIGURE 1.22
Problem 3.
FIGURE 1.20
Problem 1.
2. During the construction of the Eads bridge across the Mississippi
river at St. Louis in 1873, Theodore Cooper, a young assistant civil
engineer, slipped on a loose board and fell 90. ft into the river
(Figure 1.21). He later reported that, during the fall, he rolled
himself into a ball and rapidly calculated the velocity with which
he would hit the water. After a deep plunge, he came to the surface
still clutching his pencil and was rescued by a nearby boat.
Neglecting air resistance, determine (a) how long it took him to
fall 90. ft, and (b) the velocity with which he hit the water.
3. If 1 gallon has a volume of 0.1337 ft 3 , then how many
mouthfuls of water are required to fill the moat of a castle that
is 1.0 pole deep, 1.0 fathom wide, and 1.0 furlong long
(Figure 1.22)? Note: 1.0 pole = 12 cubits = 18 feet, and
1.0 fathom = 4.0 cubits = 6.0 feet.
4. The gauge of shotguns is universally expressed as the number of
spheres of the diameter of the bore of the gun that can be cast
from 1 lb of lead (Figure 1.23). This standardization procedure
came from the English Gun Barrel Proof Act of 1868. Taking the
density of the lead as 705 lbm/ft 3 , develop a formula relating
the diameter of the gun barrel to the gauge of the gun. Compute
the barrel diameters for 20. gauge, 12. gauge, and 10. gauge
shotguns. (Note that the caliber of a gun is not the same as its
gauge. The caliber of a weapon is just the diameter of the bore
FIGURE 1.23
Problem 4.
expressed in inches multiplied by 100. For example, a .38 caliber
pistol has a bore diameter of 0.38 inch).
5. If lead is measured in avoirdupois ounces and silver is measured in
troy ounces, which weighs more (a) an ounce of lead or an ounce
of silver, and (b) a pound of lead or a pound of silver (Figure 1.24)?
FIGURE 1.24
Problem 5.
One pound of lead
One pound of silver
Which one weighs more?
Eads Bridge
517 feet
90 feet
FIGURE 1.21
Problem 2.