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Unformatted text preview: magnitude but opposite in direction.
F) The centripetal force of the earth on the astronaut in orbit is zero.
G) The earth's gravitation force is balanced by the centrifugal force on the astronaut.
H) Since the spaceship is above the atmosphere, no air presses down on the astronaut.
4. An airplane engine starts from rest; and 2 seconds later, it is rotating with an angular
speed of 420 rev/min. If the angular acceleration is constant, how many revolutions does
the propeller undergo during this time?
θ = 1 (ω + ω 0 )t = 1 ( 420 rev/min)( 30 min) = 7.0
5. A hollow sphere of radius 0.25 m is rotating at 13 rad/s about an axis that passes
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