The Devonian is a(n)
a. epoch.
b. era.
c. eon.
d. period.
d
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Which of the following methods used to determine the mass of a cluster of galaxies does not depend on Newton's law of gravity?
A) measuring the amount of distortion caused by a gravitational lens B) measuring the temperature of X-ray gas in the intracluster medium C) measuring the orbital velocities of galaxies in the cluster D) none of the above
The hydrogen lines of spectral type A main sequence stars are ____
a. the strongest b. the weakest c. the most narrow d. useful in determining apparent magnitude e. used to estimate the luminosity of the star
Graphical Interpretation of Work: A force acts on an object, causing it to move parallel to the force. The graph in the figure shows this force as a function of the position of the object. How much work does the force do as the object moves from 4 m to 6 m?
A. 20 J B. 30 J C. 0 J D. 40 J E. 70 J
The neap tides can only occur when the Moon's position is at or near one of its orbital nodes
a. True b. False Indicate whether the statement is true or false