Harmonic excitation refers to a sinusoidal external force of a certain frequency applied to a system. ... Resonance occurs when the external excitation has the same frequency as the natural frequency of the system. It leads to large displacements and can cause a system to exceed its elastic range and fail structurally.
Did not engineer cables factoring wind shear
Answer:
D.All of the above
Explanation:
Properties of hydrogen:
1.It is lighter than air.It has density about 0.089 g/L.
2.Hydrogen rapidly change from liquid state to gas,so special protection is required to protect it.
3.It is highly flammable gas.
4.Liquid form of hydrogen exits at -432 F .This is very low temperature so special protection requires to keep it in liquid form.
Answer:
The metal Harvey should use for reflective coatings in telescope mirror is;
C. Aluminum
Explanation:
In a telescope, the mirror of the telescope is usually made of a temperature-resistant and strong glass, while the reflective coating of the mirrors is made usually from aluminum. A protective coating often composed of silicon dioxide is placed n the top of the reflective coating
Aluminum is used in a telescope, rather than the silver, which is the most reflective material, because silver requires special conditions to be able to work, and silver tarnishes when exposed to air containing sulfur, and silver is susceptible to corrode.
