document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=745513>Question 745513</A>: <I><SPAN STYLE=\"word-break: break-all;\"> THE HEIGHT OF THE ROCKET AFTER t SECONDS WHEN FIRED STRAIGHT UP WITH AN INITIAL SPEED OF 150FT PER SECOND FROM AN INITIAL HEIGHT OF 2 CAN BE MODELED BY THE FUNCTION:  s(t)=-16t^2+150t+2\r<BR>\n" );
document.write( "\n" );
document.write( "WHEN WILL THE ROCKET BE 300ft?<BR>\n" );
document.write( "WHAT IS THE MEANING OF THE Y INTERCEPT<BR>\n" );
document.write( "WHEN WILL IT REACH THE GROUND?\r<BR>\n" );
document.write( "\n" );
document.write( "I AM UNSURE OF HOW TO START THE PROBLEM. DO I USE THE QUADRATIC FORMULA?  <BR>\n" );
document.write( " </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #453868 by </B><A HREF=/tutors/aboutme.mpl?userid=rothauserc><B>rothauserc(4718)</B></A><img src=\"/images/stars/stars-13.gif\" alt=\"\" >&nbsp;<A HREF=/tutors/aboutme.mpl?userid=rothauserc><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/cgi-bin/show-face.mpl?user=rothauserc><BR>You can <A HREF=\"/cgi-bin/embed-solution.mpl?show=1&solution=453868\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> Indeed we use the given equation\r<BR>\n" );
document.write( "\n" );
document.write( "s(t)=-16t^2+150t+2\r<BR>\n" );
document.write( "\n" );
document.write( "a) when will rocket reach 300 ft<BR>\n" );
document.write( "   300 = -16t^2 + 150t + 2<BR>\n" );
document.write( "   -16t^2 + 150t - 298 = 0<BR>\n" );
document.write( "   use quadratic formula to solve<BR>\n" );
document.write( "   t = -150 plus or minus sqrt(150^2 - 4(-16)-298) / (-16*2)\r<BR>\n" );
document.write( "\n" );
document.write( "b) note if t = 0 then s = 2  which is the initial distance\r<BR>\n" );
document.write( "\n" );
document.write( "c) when will it reach the ground<BR>\n" );
document.write( "   to answer this we use the first derivative which is<BR>\n" );
document.write( "   -32t+150 and<BR>\n" );
document.write( "    t <75/16<BR>\n" );
document.write( "    so the rocket has a maximum height at (75/16, s(75/16))<BR>\n" );
document.write( "    now we want to know when it will reach the ground, this is just<BR>\n" );
document.write( "    2 * 75/16 or 75/8 = 9.38 seconds\r<BR>\n" );
document.write( "\n" );
document.write( "a nifty free math calculator program for windows is \"speedcrunch\"  :-)\r<BR>\n" );
document.write( "<BR>\n" );
document.write( "\n" );
document.write( " </SPAN>\n" );
document.write( "</TD></TR></TABLE>\n" );