problem02_90 solution

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

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2.90: a) Suppose that Superman falls for a time t , and that the student has been falling for a time t 0 before Superman’s leap (in this case, t 0 = 5 s). Then, the height h of the building is related to t and t 0 in two different ways: 2 0 2 1 gt t v h y - = - ( 29 , 2 1 2 0 t t g + - = where v 0 y is Superman’s initial velocity. Solving the second t gives . 0 2 t t g h - = Solving the first for
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Unformatted text preview: v y gives v y = , 2 t g t h +-and substitution of numerical values gives t = 1.06 s and v y = 165 s m , with the minus sign indicating a downward initial velocity. b) c) If the skyscraper is so short that the student is already on the ground, then . m 123 2 1 2 = = gt h...
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