A steel wire hangs from a high-altitude balloon. The steel has unit weight of 77 kN/m3 and yield stress of 280 MPa. The required factor of safety against yield is 2.0. The maximum permissible length of the wire is approximately:
(A) 1800 m
(B) 2200 m
(C) 2600 m
(D) 3000 m
(A) 1800 m
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Consider a situation where you exert a force F on a crate of mass m, moving it at a speed v a distance d across a floor in a time interval t.The kinetic energy of the crate is __________
Fill in the blank(s) with correct word
Where the optic nerve penetrates the eye
A. Astigmatism |
B. Eye Dominance |
C. Focus |
D. Blind Spot |
E. Color Blindness |
F. Afterimages |
An interpretation of the photoelectric effect is that:
1.Light is emitted only when electrons change orbits. 2.Light has a wavelike character. 3.Light is absorbed in quanta of energy E = h? 4.Electrons have an associated wave having wavelength ? = h/p. 5.Photons must have some minimum energy to penetrate a material. 6.More than one of the above
Which of the following is not evidence for dark matter?
A) gravitational lensing around galaxy clusters B) X-ray observations of hot gas in galaxy clusters C) the broad absorption lines found in the spectra of elliptical galaxies D) the flat rotation curves of spiral galaxies E) the expansion of the universe