Supernovae are ____
a. very common: there are thousands of detectable events occurring in our galaxy each year
b. common: a few dozen are detected in our galaxy each year
c. uncommon: there are only one or two detected in our galaxy each year
d. rare: only one or two occur each century in our galaxy
e. extremely rare: only one or two are detected in the Universe each decade
d
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A stepped steel shaft (G 5 75 GPa) with diameters d1 5 36 mm and d2 5 32 mm is twisted by torques T at each end. Segment lengths are L1 5 0.9 m and L2 5 0.75 m. If the allowable shear stress is 28 MPa and maximum allowable twist is 1.8°, the maximum permissible torque is approximately:
(A) 142 N?m
(B) 180 N?m
(C) 185 N?m
(D) 257 N?m
Which of the following factors could explain a gradual warming trend in a planet's climate?
A) a decreasing albedo B) a decrease in the amount of greenhouse gases C) a decrease in the brightness of the Sun D) a major volcanic eruption that increases the albedo of the planet by making clouds E) none of the above
An electron has a kinetic energy that is twice its rest energy. Determine its speed.
A. 0.76c B. 0.81c C. 0.94c D. 0.54c E. 0.87c
Conservation of Momentum: A 14-cm diameter champagne bottle rests on its side on top of a frictionless horizontal table. Suddenly, the cork pops and the bottle slides backward, covering a distance of 22.0 cm in 0.44 s. If the mass of the bottle is 500 times the mass of the cork, find the distance from the original position that the cork will land on the table. Neglect air resistance and assume that the cork is very small compared to the bottle.
A. 3000 cm B. 60 m C. 85 m D. 8.5 cm