Although it hasn't been observed (yet), why do astronomers think that the Milky Way may contain "dark" material?
A. Due to its large size, the light from stars on the other side of the Milky Way has not reached us yet.
B. Astronomers have detected neutrinos from unseen sources.
C. Theory predicts that there should be more black holes than we've so far detected.
D. The Galaxy's gravity seems too big for the mass astronomers can see.
Answer: D
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The speed of light changes when it goes from ethyl alcohol (n = 1.36) to carbon tetrachloride (n = 1.46). The ratio of the speed in carbon tetrachloride to the speed in ethyl alcohol, v2/v1, is
a. 1.99 b. 1.07 c. 0.932 d. 0.511 e. 0.760
A source of light is at a temperature of 1000°C. Its temperature is then increased to 2000°C, Increasing the temperature causes the peak intensity wavelength to
A) triple. B) halve. C) decrease but not quite halve. D) double. E) more than double.
A satellite in an elliptical orbit travels at a
1) constant speed 2) variable speed 3) not enough information to say because 4) the net force acting on it is zero. 5) of the component of gravitational force existing in its direction of motion. 6) it is characteristic of it to do so. 7) again, not enough information is given to say.
Assuming a linear velocity distribution and a linear temperature distribution in the boundary layer over a flat plate, derive a relation between the thermal and hydrodynamic boundary-layer thicknesses and the Prandtl number.
GIVEN
Boundary layer over a flat plate
FIND
A relation between the thermal and hydrodynamic boundary-layer thicknesses and the Prandtl number
ASSUMPTIONS
Linear velocity and temperature distributions in the boundary layers
SKETCH
