A board of mass m lies on the ground. What is the magnitude of the force you would have to exert to lift one end of the board barely off the ground (assuming that the other end still touches the ground)?
A. 
B. 
C. 
D. The answer depends on the board’s length.
E. Other (explain)
C.
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An observer on Earth's equator would find
a. Polaris directly overhead. b. Polaris 40° above the northern horizon. c. Polaris on the northern horizon. d. the celestial equator passing directly overhead. e. that the ecliptic coincides with the horizon.
Why are remote sites chosen for ground-based telescopes?
A. Populated areas produce light pollution that degrades the quality of observations. B. Deserts and mountaintops tend to be cloud-free, making observations convenient. C. Remote areas have less interference from power lines and other sources of noise. D. Mountaintops allow astronomers to avoid morning hazes. E. All of these choices are correct.
How many significant figures are in 0.0037010?
A) four B) five C) six D) seven E) eight
Characteristic x-ray spectra come from