A window washer pulls herself upward using the bucket–pulley apparatus shown in the Fig.
(a) How hard must she pull downward to raise herself slowly at constant speed?
(b) If she increases this force by 15%, what will her acceleration be?
Answer:
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Spiral galaxy rotation curves are generally fairly flat out to large distances. Suppose that spiral galaxies did not contain dark matter. How would their rotation curves be different?
A) The orbital speeds would fall off sharply with increasing distance from the galactic center. B) The orbital speeds would rise upward with increasing distance from the galactic center, rather than remaining approximately constant. C) The rotation curve would be a straight, upward sloping diagonal line, like the rotation curve of a merry-go-round. D) The rotation curve would look the same with or without the presence of dark matter.
A 1.500 m long uniform beam of mass 30.00 kg is supported by a wire as shown in the figure. The beam makes an angle of 10.00 degrees with the horizontal and the wire makes and angle of 30.00 degrees with the beam. A 50.00 kg mass, m, is attached to the end of the beam. What is the tension in the wire?
A. 2,034 N
B. 1,855 N
C. 1,435 N
D. 1,255 N
E. 1,035 N
Which of the following quantities is directly proportional to the time interval after a projectile has left the barrel that shot it out? The x axis is horizontal; the y axis is vertically upward.
A.
B.
C.
D.
E.
Dr. X believes that the Hubble constant is H0 = 20 km/s/Mly while Dr. Y believes it is H0 = 24 km/s/Mly. Which statement below automatically follows?
A) Dr. X believes that the universe is expanding, but Dr. Y does not. B) Dr. X believes that the universe is older than Dr. Y believes. C) Dr. X believes that the universe has a much higher density than Dr. Y believes. D) Dr. X believes that the universe will someday stop expanding, while Dr. Y believes it will expand forever. E) Dr. X believes that the Andromeda Galaxy (a member of our Local Group) is moving away from us at a slower speed than Dr. Y believes.