As a gust of wind blows across a field of grain, a wave can be seen to move across the field as the tops of the plants sway back and forth. This wave is a:
a. transverse wave.
b. longitudinal wave.
c. polarized wave.
d. interference of waves.
b
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The water flowing over Niagara Falls drops a distance of 50. m. Assuming that all the gravitational energy is converted to thermal energy, by what temperature does the water rise?
What will be an ideal response?
Carbon-fiber reinforced epoxy is being used as the outer surface material in high-performance aircraft where the surface temperatures are elevated because of the friction with air. The maximum-use temperature for epoxy resin is approximately 260°C. A composite sheet is produced from 75 vol % carbon fiber and 25 vol % epoxy resin. Assume that the epoxy and carbon are stress free at room temperature, and the composite is heated from room temperature (22°C) to 260°C during service. The elastic modulus of the carbon fiber is 380 GPa, the ultimate tensile strength is 2.4 GPa, and the axial thermal expansion coefficient is –0.7×10-6 K-1 . The elastic modulus of the epoxy resin is 4 GPa, the ultimate tensile strength is 0.07 GPa, and the thermal expansion coefficient is 60×10-6 K-1 .
(a) Calculate the thermal stresses, both the magnitude and sign, in the epoxy matrix and in the carbon fibers at 260°C. Assume that each material is elastic at all temperatures, and that there is good interface bonding. (b) Calculate the composite strain in heating from 22°C to 260°C. (c) Is there any component of this design that might cause a problem? Comment on the results in comparison to the data provided. If data is not available on these components, justify your evaluation of this design based upon your knowledge of these materials.
The isotope 64Zn has a nuclear radius of 4.8 × 10^?15 m. Approximately what is the nuclear radius of the isotope 27Al?
a. 2.0 × 10^?15 m b. 2.7 × 10^?15 m c. 3.6 × 10^?15 m d. 4.0 × 10^?15 m
How does energy relate to the way that streams meander?
What will be an ideal response?