A motor drives a shaft with diameter d 5 46 mm at f 5 5.25 Hz and delivers P 5 25 kW of power. The maximum shear stress in the shaft is approximately:
(A) 32 MPa
(B) 40 MPa
(C) 83 MPa
(D) 91 MPa
(B) 40 MPa
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For dilute concentrations of point defects, the scattering distance for free electrons is _________related to the concentration of point defects.
Fill in the blank(s) with the appropriate word(s).
Voltage produced by a generator alternates because
A) it produces pulses of current. B) the magnetic field that produces it alternates. C) alternations in the mechanical energy input. D) effectively it is an ac motor in reverse. E) the current it produces alternates.
A rock, released at rest from the top of a tower, hits the ground after 3.5 s. What is the speed of the rock as it hits the ground? (g = 9.8 m/s2 and air resistance is negligible)
a. 34 m/s b. 17 m/s c. 44 m/s d. 68 m/s e. 24 m/s
Ehrenfeld (119) argues that nonresources should be conserved. By this he means that conservation cannot and should not rely on economic or ecological justifications
He thinks that each species on the Earth, evolved over millions of years, is natural art, and that a species lost is permanently gone. He asks: "What sort of change in the world view would favor the conservation of nonresources? Nothing less than a rejection of the heroic, Western ethic with its implicit denial of man's biological roots and evolved structure." Comment on Ehrenfeld's ideas.