document.write( "Question 1164162: A lizard jumps stright up from the ground. The lizard lands on a leaf that was directly above where it jumped from. Although the lizard jumped upward with an initial velocity of +8m/s, when he landed on the leaf his final velocity was just -2m/s\r
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Algebra.Com's Answer #788466 by ikleyn(52908) $\"\"$ $\"About$

You can put this solution on YOUR website!
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\n" ); document.write( "\n" ); document.write( " Let me show you how a physicist will solve this problem.\r
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document.write( "To answer question (a), the physicist writes the energy conservation law equation\r\n" );
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document.write( "    mgh =  - \r\n" );
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document.write( "saying the the potential energy increment mgh is the difference of the initial kinetic energy and the final kinetic energy.\r\n" );
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document.write( "Here m is the mass of the lizard, which we can cancel in both sides of the equation;\r\n" );
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document.write( "g is the gravity acceleration, g = 9.81 m/s^2, or 10 m/s^2 , approximately;\r\n" );
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document.write( "h is the difference of the levels  (= \"how high above the ground\");\r\n" );
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document.write( "  and    are the given velocities.\r\n" );
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document.write( "So, after canceling the mass \"m\" in both sides and substituting the given data, we get\r\n" );
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document.write( "    10h =  -  =  -  = 32 - 2 = 30\r\n" );
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document.write( "      h                                     = 30/10 = 3.\r\n" );
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document.write( "So, the answer to the first question is \"the leaf is 3 meters above the ground\".\r\n" );
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document.write( "To answer question (b), physicist will use the base equation for a uniformly accelerated/decelerated move\r\n" );
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document.write( "     v = gt,\r\n" );
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document.write( "where v is velocity and t is the time (\"g\" is just introduced above).\r\n" );
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document.write( "The time for flying vertically up from the ground to the upperst possible height (till stop) is  \r\n" );
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document.write( "    t =  =  = 0.8 seconds.\r\n" );
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document.write( "The time for falling down from the upperst height to get the speed of 2 m/s is\r\n" );
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document.write( "    t =  =  = 0.2 seconds.\r\n" );
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document.write( "The total time flying up and down is, thus,  0.8 + 0.2 = 1 second.\r\n" );
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