problem06_69

University Physics with Modern Physics with Mastering Physics (11th Edition)

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6.69: a) N 147 . 0 kg) 120 . 0 ( m) 40 0 ( m/s) (0.70 rad 2 2 = = = = . R v m ma T , or 0.15 N to two figures. b) At the later radius and speed, the tension is N 41 . 9 kg) 120 . 0 ( m) 10 0 ( m/s) (2.80 2 = . , or 9.4 N to two figures. c) The surface is frictionless and horizontal, so the net work is the work done by the cord. For a massless and frictionless cord, this is the same as the work done by the person, and is equal to the change in the block’s kinetic energy,
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Unformatted text preview: J 441 . ) ) s / m 70 . ( ) s / m 80 . 2 )(( kg 120 . )( 2 / 1 ( ) ( ) 2 / 1 ( 2 2 2 1 2 2 1 2 =-=-=-v v m K K . Note that in this case, the tension cannot be perpendicular to the block’s velocity at all times; the cord is in the radial direction, and for the radius to change, the block must have some non-zero component of velocity in the radial direction....
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This document was uploaded on 02/04/2008.

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