1112Assignment 2_sol

1112Assignment 2_sol - College Physics I 2011/12 Assignment...

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College Physics I 2011/12 Assignment 2 Suggested solutions 1. A body of mass m 1 + m 2 is split into two parts of masses m 1 and m 2 by an internal explosion which generates kinetic energy K . If the two parts move in the same line after the explosion, show that the speed of one part relative to the other is 2 1 2 1 ) ( 2 m m m m K + Conservation of mechanical energy and momentum give: 2. A 62-kg bungee jumper jumps from a bridge. She is tied to a bungee cord whose unstretched length is 12 m, and falls a total of 31 m. (a) Calculate the spring stiffness constant k of the bungee cord, assuming Hooke’s law applies. (b) Calculate the maximum acceleration she experiences. (a) The mechanical energy of the jumper is conserved. Use y for the distance from the 0 of gravitational PE and x for the amount of bungee cord “stretch” from its unstretched length. Subscript 1 represents the jumper at the start of the fall, and subscript 2 represents the jumper at the lowest point of the fall. The bottom of the fall is the zero location for gravitational PE ( 29 0 y = , and the location where the bungee cord just starts to be stretched is the zero location for elastic PE ( 29 0 x = . We have 1 0 v = ,
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1 31 m y = , 1 0 x = , 2 0 v = , 2 0 y = , and 2 19 m x = . Apply conservation of energy. ( 29
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This note was uploaded on 02/22/2012 for the course CHEM yscn0027 taught by Professor Drtong during the Fall '10 term at HKU.

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1112Assignment 2_sol - College Physics I 2011/12 Assignment...

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