You are asked to select a material for a container on a ship for liquified natural gas that will be at –163°C (–260°F). For the classes of metals, ceramics, polymers, and composites give the advantages and disadvantages of the best possible material within each class of material for this design based upon subjects you have studied in Chapters 1 to 4 in this book. For example you may decide that carbon fiber reinforced epoxy is the best possible composite material for this design. Give the advantages and disadvantages of carbon fiber reinforced epoxy for this design.
What will be an ideal response?
Metals
The best possible metal is stainless steel
Advantages of stainless steel
Ductile and resistant to fracture
Low thermal conductivity
Known manufacturing processing
High strength
Disadvantages of stainless steel
High cost
Ceramics:
There is no suitable ceramic material because all ceramics have brittle fracture
Polymers:
All polymers are brittle at this temperature and they are of low strength.
Composites:
Glass fiber reinforced epoxy would probably be a better choice for a large liquid
container than carbon fiber reinforced epoxy because of the high cost of carbon fiber.
Advantages of glass reinforced epoxy:
Low thermal conductivity
Lower density than stainless steel
High strength
Disadvantages of glass reinforced epoxy
Resistance to fracture may not be as high as stainless steel
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The satellite Amalthea orbits Jupiter at just about the same distance in kilometers at which Mimas orbits Saturn. Yet Mimas takes almost twice as long to orbit
What can you deduce from this difference qualitatively? Since Jupiter and Saturn are not very different in radius, what else can you conclude?
A long steel rod (2 cm in diameter, 2-m-long) has been heat-treated and quenched to a temperature of 100°C in an oil bath. To cool the rod further, it is necessary to remove it from the bath and expose it to room air. Will the faster cool-down result from cooling the cylinder in the vertical or horizontal position? How long will the two methods require to allow the rod to cool to 40°C in 20°C air?
GIVEN • A long steel rod in air • Diameter (D) = 2 cm = 0.02 m • Length (L) = 2 m • Initial temperature (Ts,i) = 100°C • Air temperature (T?) = 20°C FIND (a) Is it faster to cool the rod vertically or horizontally? (b) Time for rod to cool to 40°C in each position ASSUMPTIONS • Steel is 1% carbon PROPERTIES AND CONSTANTS for 1% carbon steel Thermal conductivity (ks) = 43 W/(m K) Specific heat (c) = 473 J/(kg K) Density (?) = 7801 kg/m3 for dry air at the initial mean temperature of 60°C Thermal expansion coefficient (?) = 0.003 1/K Thermal conductivity (k) = 0.0279 W/(m K) Kinematic viscosity (?) = 19.4 × 10–6 m2/s Prandtl number (Pr) = 0.71
The slowing of clocks in strongly curved space time is known as
a. gravitational radiation. b. time dilation. c. gravitational curvature. d. gravitational redshift. e. hyperspace drag.
What does Hubble's law imply about the history of the universe?
A) The universe must be infinitely old and huge. B) The universe had a beginning and has expanded since, giving it a finite age. C) The Milky Way lies exactly at the center of this expansion. D) The redshifts will lengthen with time due to dark energy. E) The redshifts will turn to blue shifts as universe contraction follows the expansion.