document.write( "Question 58464This question is from textbook Algebra structure and Method
\n" ); document.write( ": a rocket is fired upward with an inital speed of 1960 m/s. after how many minutes does it hit the ground? \n" ); document.write( "
Algebra.Com's Answer #40047 by Edwin McCravy(20060)\"\" \"About 
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a rocket is fired upward with an inital speed of \r\n" );
document.write( "1960 m/s. after how many minutes does it hit the \r\n" );
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document.write( "The formula is\r\n" );
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document.write( "             s = sO + vOt + gt2/2\r\n" );
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document.write( "Since it starts from the ground, sO = 0\r\n" );
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document.write( "Since it ends up on the ground, s = 0\r\n" );
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document.write( "Since its initial speed is 1960 m/s upward, \r\n" );
document.write( "vO = 1960\r\n" );
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document.write( "Since it is fired on earth, rather than on the \r\n" );
document.write( "moon or Mars, g = -9.8 m/s2\r\n" );
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document.write( "Plug these all into:\r\n" );
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document.write( "             s = sO + vOt + gt2/2\r\n" );
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document.write( "             0 = 0 + 1960t + (-9.8)t2/2\r\n" );
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document.write( "       9.8t2/2 = 1960t\r\n" );
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document.write( "Multiply both sides by 2 to clear of fractions\r\n" );
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document.write( "         9.8t2 = 3920t\r\n" );
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document.write( " 9.8t2 - 3920t = 0\r\n" );
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document.write( "t(9.8t - 3920) = 0\r\n" );
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document.write( "Setting the first factor = 0\r\n" );
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document.write( "             t = 0\r\n" );
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document.write( "Setting the second factor = 0\r\n" );
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document.write( "   9.8t - 3920 = 0\r\n" );
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document.write( "          9.8t = 3920\r\n" );
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document.write( "             t = 3920/9.8\r\n" );
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document.write( "             t = 400 seconds or 6 2/3 minutes, or \r\n" );
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document.write( "6 minutes 40 seconds.\r\n" );
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document.write( "So the rocket is on the ground at time 0 \r\n" );
document.write( "(at lift-off), which is why we get t = 0 as one \r\n" );
document.write( "solution. Then the rocket is again on the ground \r\n" );
document.write( "6 2/3 minutes later, which is the solution we\r\n" );
document.write( "are looking for.\r\n" );
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document.write( "Edwin
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