Future space stations will create an artificial gravity by rotating. Consider a cylindrical space station of 380 m diameter rotating about its axis. Astronauts walk on the inside surface of the space station
What rotation period will provide "normal" gravity? A) 28 s
B) 39 s
C) 6.2 s
D) 4.4 s
A
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A basketball player jumps to make a basket, and remains in the air for a moment. A sportscaster, talking about the game, then remarks that she has "defied gravity." Which of the following accurately describes the situation?
A) The player did stay in the air in spite of the Law of Gravitation, but a single counter-observation is not enough to warrant revisiting a theory that usually works. B) The player produced enough force with her legs to accelerate up into the air, and gravity brought her back down with an acceleration of 9.8 m/s2. C) The player only seemed to defy gravity, but part of the Universal Law of Gravitation makes an exception for basketball players. D) The player has defied gravity, so scientists must go back into the lab to refine their theory.
A solid sphere is rolling without slipping along a horizontal surface with a speed of 5.50 m/s when it starts up a ramp that makes an angle of 25.0° with the horizontal. What is the speed of the sphere after it has rolled 3.00 m up the ramp?
A) 4.01 m/s B) 8.02 m/s C) 1.91 m/s D) 2.16 m/s E) 3.53 m/s
Emission nebulae like M42 occur only near stars that emit large amounts of
A) infrared heat. B) X-rays and gamma rays. C) microwaves. D) ultraviolet radiation. E) visible light.
A bucket of water with total mass 21.0 kg is attached to a rope, which in turn is wound around a 0.050-m radius cylinder, with crank, at the top of a well. The moment of inertia of the cylinder and crank is 0.21 kg m2 . The bucket is raised to the top of the well and released to fall back into the well. What is the kinetic energy of the cylinder and crank at the instant the bucket is moving with
a speed of 5.4 m/s? a. 4.8E+2 J b. 1.2E+3 J c. 3.1E+2 J d. 1.2E+4 J