document.write( "Question 58463This question is from textbook Algebra structure and Method
\n" ); document.write( ": a ball is thrown upward with an initial speed of 24.5 m/s. When is it 19.6 m high? (two answers) \n" ); document.write( "
Algebra.Com's Answer #40050 by Edwin McCravy(20060)\"\" \"About 
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document.write( "A ball is thrown upward with an initial speed of \r\n" );
document.write( "24.5 m/s. When is it 19.6 m high? (two answers)\r\n" );
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document.write( "The formula is \r\n" );
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document.write( "                   s = sO + vOt + at2/2\r\n" );
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document.write( "Since its initial speed is 24.5 m/s upward, sO = 24.5\r\n" );
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document.write( "Since we assume it starts on the ground, sO = 0\r\n" );
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document.write( "Since we want to know when its distance is 19.6 m, \r\n" );
document.write( "s = 19.6\r\n" );
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document.write( "Since we know that the acceleration is due to \r\n" );
document.write( "gravity, and that the ball is thrown up on Earth,\r\n" );
document.write( "(and not on the moon or Mars), then a = g = -9.8 m/s2. \r\n" );
document.write( "So a = -9.8.\r\n" );
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document.write( "Plug these into\r\n" );
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document.write( "                   s = sO + vOt + at2/2\r\n" );
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document.write( "                19.6 = 0 + 24.5t + (-9.8)t2/2 \r\n" );
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document.write( "                19.6 = 24.5t - 4.9t2\r\n" );
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document.write( "4.9t2 - 24.5t + 19.6 = 0\r\n" );
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document.write( "Clear of decimals by multiplying through by 10,\r\n" );
document.write( "that is, by moving the decimals one place to the\r\n" );
document.write( "right in all the terms.\r\n" );
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document.write( "  49t2 - 245t + 196 = 0\r\n" );
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document.write( "Divide all terms by 49\r\n" );
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document.write( "        t2 - 5t + 4 = 0\r\n" );
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document.write( "Factor the trinomial on the left sides:\r\n" );
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document.write( "     (t - 4)(t - 5) = 0\r\n" );
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document.write( "Setting the first factor = 0\r\n" );
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document.write( "              t - 4 = 0\r\n" );
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document.write( "                  t = 4 seconds\r\n" );
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document.write( "Setting the second factor = 0\r\n" );
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document.write( "              t - 5 = 0\r\n" );
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document.write( "                  t = 5 seconds\r\n" );
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document.write( "So it reaches the height of 19.6 m after 4 seconds\r\n" );
document.write( "(on its way up) and again after 5 seconds (on its\r\n" );
document.write( "way down).\r\n" );
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document.write( "Edwin
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