How did scientists first prove that light had a finite speed?
a. By measuring how long it takes for a second observer to be seen uncovering a lantern on a distant mountain in response to the first observer uncovering a lantern.
b. By measuring how long it took to see lightning during a thunderstorm.
c. By measuring how fast a notched wheel must rotate for light passing through one notch to be reflected from a distant mirror back through the next notch.
d. By measuring how fast a multi-faced mirror must rotate for light reflected from one mirror face to be reflected from a distant mirror to reflect back from the next face.
e. By measuring how the revolution of the moons of Jupiter appears longer when they are farther from Earth.
e
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Which law explains why a skater can spin faster by pulling his arms closer to his body, or spin slower by spreading his arms out?
A) the law of gravity B) Newton's third law of motion C) the law of conservation of momentum D) the law of conservation of angular momentum E) the law of conservation of energy
A mass src="https://sciemce.com/media/4/edf57f6e1d0acd4635.png" class="w-image" />?
is connected by a light string that passes over a pulley of mass M to a mass 
as shown in the figure. Both masses move vertically and there is no slippage between the string and the pulley. The pulley has a radius of 30.0 cm and a moment of inertia of 
If 
is 4.00 kg, 
is 3.00 kg and M is 6.00 kg, then what is the tension in the string that is attached to
A. 20.7 N
B. 25.5 N
C. 31.7 N
D. 35.2 N
E. 41.3 N
What type of object is believed to be the central source of energy for an active galaxy?
A. globular cluster B. a large amount of gas and dust C. an unusually large and bright main sequence star D. a massive black hole
A column that extends from sea level to the top of the atmosphere contains a certain mass of air. If the column instead contained the same mass of mercury, its height would be about
A) 3/4 meter. B) 10.3 meters. C) 5.6 kilometers. D) none of the above