Modern Engineering Thermodynamics

Problems 31
49. Using the CGS units system, determine the kinetic energy
of an automobile weighing 1.60 billion dynes traveling at
3000. cm/s.
50. Using the CGS units system, determine the potential energy of
a truck weighing 27.0 billion dynes at a height of 30.0 × 10 3 cm
at standard gravity.
51. Using the Absolute English units system, determine the weight
of an object whose kinetic energy is 306.2 ft·poundal, when it is
traveling at a velocity of 10.0 ft/s.
52. Using the Absolute English units system, determine the kinetic
energy of an object traveling at 15.3 ft/s and weighing
40.0 poundal at standard gravity.
53. Using the Absolute English units system, determine the potential
energy of an object weighing 200. lbm· ft/s 2 at a height of
3000. ft at standard gravity.
54. Using the Technical English units system, determine the mass of
an object having a potential energy of 705 ft·lbf when it is at a
height of 25.0 ft at standard gravity.
55. Using the Technical English units system, determine the
kinetic energy of a 197 slug mass traveling at a velocity
of 33.5 ft/s.
56.* Micrometeoroids have space station impact velocities of
19.0 km/s. Determine the impact kinetic energy in SI and
Engineering English units of a 1.00 g micrometeoroid traveling
at this velocity.
57. A 2000. lbm meteoroid has a velocity of 23.0 × 10 3 mph
(Figure 1.31). Determine the kinetic energy of the meteoroid in
Engineering English and SI units.
windings). If the motor shaft has a mass of 150. kg and a
diameter of 0.250 m, and the armature windings have a mass of
600. kg and an outside diameter of 1.50 m (the inside diameter
is the same as the outside diameter of the shaft), determine the
rotational kinetic energy stored in the motor when it is rotating
at 3600. rpm.
61. A 0.3125 lbm baseball 2.866 inches in diameter is thrown
with a velocity of 80.0 mph and it simultaneously spins
about its axis at 5.00 rad per second (Figure 1.32). Determine
the total (translational plus rotational) kinetic energy of
the ball.
FIGURE 1.32
Problem 61.
5.00 radians/s
80.0 mph
62. A 12 lbm bowling ball 8.59 inches in diameter is given a spin
of 1.0 revolution per second while traveling down the lane at
17 ft per second (Figure 1.33). Determine the total translational
plus rotational kinetic energy of the ball.
17 ft/s
1.0 rev/s
FIGURE 1.31
Problem 57.
58.* The Sandia National Laboratory hypervelocity two-stage light gas
gun achieved muzzle velocities of 12.0 km/s with 0.500 g flat
plate projectiles. Determine the muzzle kinetic energy of the
projectiles in SI and Engineering English units.
59.* A thin disk with a diameter of 1.00 m and weighing 8.00 kg is
spun about its axis at 30.0 × 10 3 revolutions per minute.
Determine its rotational kinetic energy.
60.* The armature of a large electric motor can be thought of as
being composed of a slender solid circular rod (the motor drive
shaft) inside a large hollow circular cylinder (the armature
FIGURE 1.33
Problem 62.
63.* The NASA space shuttle’s main engine high-pressure
turbopump rotors are cryogenically spin tested in a vacuum
at 40.0 × 10 3 rpm and –195°C. The rotor can be modeled as
athindisk0.600mindiameterwithaneffectivemassof
8.50 kg. Determine the rotational kinetic energy of the rotor
about its axis of rotation when it is running at the test
speed.
64. A great deal of research has been carried out at the Oak
Ridge National Laboratory in Tennessee on flywheel energystorage
systems. The lab developed a 27.0-inch diameter
composite flywheel that can run at 40.0 × 10 3 rpm on