Physics 115 Test 2A with key


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Unformatted text preview: In which direction is her apparent weight? a. b. c. d. direction (a) direction (b) direction (c) direction (d) (b) (d) Answer (d) (c) See book Fig. 3.3.4 and its discussion. Summarizing: Apparent weight = feeling of acceleration + gravitational weight (vector su m!) Acceleration is to the left so feeling of acceleration is to the right Gravitational weight is m x g and points down Now vector addition of something to the right PLUS something down gives a net effect as in (d). Question 9 – When a star runs out of nuclear fuel, gravity ma y crush it into a neutron star about 12 miles) in diameter. Although the star may have taken a year o r so to rotate once before its collapse, the neutron star rotates several times a second. What explains this dramatic increase in angular velocity? a. b. c. d. the angular momentum of the star is conserved the nuclear energy of the star does work to speed the star up the momentum of the star is conserved sliding friction in the collapsing car releases large am ounts of heat, fueling the star’s rotation Answer (a) The angular momentum is always (rotational mass) x (angular speed) and t his is conserved. Due to the collapse, the rotational mass goes down: mass moves closer to the axis of rotation....
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This document was uploaded on 02/23/2014 for the course PHYSICS 115 at UNL.

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