What is not a main source of evidence for the existence of dark matter?
A) massive blue stars
B) rotation curves of disk galaxies
C) stellar motions in elliptical galaxies
D) velocities and positions of galaxies in clusters of galaxies
E) gravitational lensing by clusters of galaxies
A
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Where would you most likely find a large radio telescope?
a. in a busy, populated area b. at the peak of a mountain c. on top of a tall building d. in a mountain valley e. near multiple radio towers
When an automobile moves with constant velocity the power developed is used to overcome the frictional forces exerted by the air and the road. If the power developed in an engine is 50.0 hp, what total frictional force acts on the car at 55 mph (24.6 m/s)? One horsepower equals 746 W
In this figure, a cork attached to a string floats in an inverted jar filled with water. Compare the cork to a helium balloon attached to a car seat. (See the "Physics on Your Own" box on page 164 of your textbook). As the jar shown here is accelerated, you would expect the cork to behave:
a. similar to the balloon in an accelerating car. b. the opposite of the helium balloon in an accelerating car. c. in a way that is unrelated to the balloon.