document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=185707>Question 185707</A>: <I><SPAN STYLE=\"word-break: break-all;\"> If an object is given an initial velocity of v0 feet per second from a height of S0 feet, then its height S after t seconds is given by the formula  <BR>\n" );
document.write( "S = -16t^2 +v0t + S0.  A rock is thrown into the air at 26 feet per second from a height of 13 feet. How long does it take to reach the earth?<BR>\n" );
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document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #139291 by </B><A HREF=/tutors/aboutme.mpl?userid=stanbon><B>stanbon(75887)</B></A><img src=\"/images/stars/stars-13.gif\" alt=\"\" >&nbsp;<A HREF=/tutors/aboutme.mpl?userid=stanbon><IMG SRC=http://www.algebra.com/images/aboutme-small.gif BORDER=0 alt=\"About Me\" VALIGN=MIDDLE></A>&nbsp;<IMG SRC=http://www.algebra.com/images/nopicture.jpg><BR>You can <A HREF=\"/cgi-bin/embed-solution.mpl?show=1&solution=139291\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> If an object is given an initial velocity of v0 feet per second from a height of S0 feet, then its height S after t seconds is given by the formula <BR>\n" );
document.write( "S = -16t^2 +v0t + S0. A rock is thrown into the air at 26 feet per second from a height of 13 feet. How long does it take to reach the earth?<BR>\n" );
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document.write( "S(t) = -16t^2 +26t + 13<BR>\n" );
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document.write( "When it reaches the earth its height is zero; solve for \"t\":<BR>\n" );
document.write( "-16t^2 +26t + 13 = 0<BR>\n" );
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document.write( "t = [-26 +- sqrt(26^2 - 4*-16*13)/(-32)\r<BR>\n" );
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document.write( "t = [-26 +- sqrt(1508)]/(-32)\r<BR>\n" );
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document.write( "Positive solution:\r<BR>\n" );
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document.write( "t = [-26 - 38.83]/(-32)\r<BR>\n" );
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document.write( "t = 2.03 seconds<BR>\n" );
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document.write( "Cheers,<BR>\n" );
document.write( "Stan H.\r<BR>\n" );
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